Research Methods Supercourse
Publish Soon, Publish Often, a Guide to Scientific Publications
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Hypotheses 
Questions 
Expert Answers 

2016 Questions  
Q24 by Avalli, November 2, 2016  I need to develop village maps of risk factors of diabetes. The risk factors will be assessed through household survey of individuals. For developing GIS maps for risk factors based on survey what should be the sample size of household in villages. Will random selection of 25% households in each village suffix to develop maps as high, moderate & low  
Q23 by Teresa, November 1, 2016  What is the quickest and best form of recruitment for a qualitative study, which requires 12 facetoface interviews? 
A23 by
Nicolas Padilla,
November 01, 2016 It depend on the study design.
All selection of participants is
nonparamethric.


Q22 by Karen, March 30, 2016  I am required to conduct an information needs analysis to determine the needs of a school community (the majority of the children come from a poor background). Which data collection tools and sampling method or methods can be used? 
A22 by
Nicolas Padilla,
March 31, 2016 The determine the needs of a schools is needed a crosssectional design. The sampling method can be simple random choice ( systematic or with random numbers).The tools to collect information depend on what you think about the needs of the MAy be on nutrition of scholarage children or obesity or health care. A22 by Ronald LaPorte, March 31, 2016 I wanted to add a few more pragmatic comments. It is always best to start with an existing survey, that has been used frequently and is directly comparable with other centers. I typically recommend a WHO survey or FAO, NHANES, Monaca, etc. If you want to add additional questions it is fine. One reason for this is that often articles are turned down if you say that you are using the "Buckle" survey that you developed to measure smoking, in contrast to the WHO Smoking survey used in 50 countries and 10,000 people.. You can easily search to find surveys that have stood the test of time. This also eliminates the need to do reliability testing for a survey that you developed as you do not need to test a survey that has been used 20000 times. I would think that in your country and others. Do a google scholar search and identify some of the authors, and just write to them to get their advice. When I was starting out I did this all the time. I would write a MOO (methods of operation). This describes exactly what you are planning to do, the hypotheses you plan to test, the data you will collect, and how you plan to analyze your data. This can be changed as the project evolves, but it serves as a template. You will find as you plan this survey that various people will come to you and say "why don't you collect this", what about this, what about a sample of adults, etc. You have to be very careful that you do not allow project drift. Project drift is where you start out a project designed for one set of objectives, and then other objectives our piled on. Having a MOO helps to prevent this.I always think that it is important to pilot test before going in to a much broader survey. Even by testing this on 40 students, you can see the problems you will run into with the much larger sample, and you can modify you protocolI always believe the shorter the survey the better. I personally like 1 page surveys if you can do this. Once you have a MOO written you can have scientists external to your center review it. As you can see, for experienced researchers, it is very important to try and iron out issues before you go into the field. This eliminates many problems. 

2015 Questions  
Q21 by Aliaa, November 17, 2015  What are the best statistical analysis methods that could be used in evaluating experiments with small sample size of experimental animals? I am working in chronic experiment in which I am facing a high mortality rate. I started with a large number of rats, but unfortunately the end surviving animals was small. I hope if you could guide me for the most appropriate statistical method for analysis of my work. 
A21 by
Nicolas Padilla,
November 24, 2015 Your statistical analysis depends on what do you want to measure. Also, it depends on type of variables that you are measuring. Survival? Kaplan Meier Curve. Do you have two groups: exposed and nonexposed and your variables are quantitative? t Student for two independent means. Are your variables categoricals and you have two groups with follow up? Risk Ratios. Are your variables categorical and you have two groups without follow up? Chisquared test and Odds Ratio. If you have a small sample size (for example, less than 50) or your quantitative variables are no Normal you can use Wilcoxon. 

Q20
by
Afiamaa March 28, 2015 
What are methodological assumptions? 
A20 by
Faina Linkov,
March 28, 2015
That's a tough question as
different types of study
methodologies generally have
different underlying
assumptions.
Overall most investigators would have assumptions pertaining to the underlying distribution if data, study heterogeneity, and characteristics of targeted population. This is a good article for case control and cohort studies description http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2998589/ You may comment to clarify the question. 

Q19 by Aliaa, February 11, 2015  What are the best conditions and the best prophylactic therapy that could be used to protect the experimental rats in a longterm (2 months duration) or chronic diabetes Study using Streptozotocin(STZ)? Is it suitable to use antimicrobial therapy as a prophylactic during such experiments? Is there any reference mentioned that issue? 
A19 by
Ronald LaPorte,
February 12, 2015
Thank you very much for your
question. I am a diabetes
researcher, but sadly not
working in the area of animal
models. When I have an important
question like this I search
google scholar for others who
have published in the area. Then
select 510 and write to them
posing your question. Typically
a few will respond as scientists
like to help colleagues. Then
you can also continue to ask
questions of that person. If no
one responds, write to another
10. You will find someone who
can help. Good luck!


2014 Questions  
Q18 by Joel Samson Ruvugo, March 31, 2014  I am in need of finding support on how to publish the literature review and what procedures to follow. 
A18 by
Ronald LaPorte, March 31, 2014
I am in need of finding support
on how to publish the literature
review and what procedures to
follow.
Writing a literature can be a
daunting task. Luckly most of
the areas where one would need
to write a literature review you
can find example. Search first
on your topic in google scholar,
and google it self. From these
you can identify review articles
that provide information. It is
best to do a systematic review.
Do a search on Systematic
reviews and this will provide
guidelines. You might consider a
Meta Analysis. We have a
wonderful lecture on Meta
Analysis in the supercourse
I personally like to do reviews
and put tables which describe
the literature. For example
something like this.
Studies examining the
relationship of Physical
Activity to bone density. With
tables like this one can
immediately see the overview of
the area. The text would then
describe the area.
Author Year
Population Type of study
relationship between PA and BD
conclusions comment
If you have not written a review
before it is good to find a
mentor. You can find mentors at
your university, also you can
find people who have published
in the area and ask them to
mentor you. In general it will
be difficult to get a full
professor to help. However, if
you find an assistant professor
who wants to help, contact them.
I would also do a search in
Youtube on "how to write a
review". I have been finding
that many of the points
presented in youtube are very
good
The end of the review will
typically consist of types of
research that can be done in the
future.
It is best initially to do
reviews in areas that are
specific to where you live. For
example a review on the
epidemiology of sand Pneumonia
would be of interest to many
people in and out of Saudi
Arabia.
After your article is written
search around to find experts
who could review it.


Q17 by Naresh T Chauhan, March 31, 2014  I am helping one of my student on conducting one study on factors delaying the diagnosis of breast cancer in tertiary care center. Kindly guide me How to proceed? I mean after doing review of literature I found that most of the researcher had taken the newly diagnosed cases from hospital for particular duration, Is there any other way to select the subject in this study. This study will be done amongst three special center diagnosing and providing treatment to cancer pt. 
A17 by
Nicolas Padilla, March 31, 2014 Depend of study design.
Maybe Cases (Breast cancer with
delaying diagnosis, por example
metastasis) Controls (breast
cancer with early diagnosis).
And to ask or to see the
registry why diagnosis was
delayed (from subject, hospital,
system etc)
A17 by Jay M. Fleisher, March 31, 2014 The control group selected is problematic (CaseControl Methodology). It ignores Length Bias and Lead Time Bias. If one looks at a group Dx with early stage Ca vs Late Stage Dx one would be ignoring the aggressiveness of the individual cancers. For example One person could be diagnosed with a early stage Ca and survive say, 8 years. While another person could be Dx at the same stage and only live one year. The latter case having a more aggressive form of tumor. I am confused at the outcome of the proposed study. Is it Survival. If so things like stage, and grade have to be factored in and one have to follow the cohort for at least 5 years. This puts us into a Prospective Cohort Design, which is costly. The proposed study is more complex than it seems. One needs to Google both Lead Time Bias and Length Bias to better understand
A17 by
Ronald LaPorte, March 31, 2014
A difficulty for
me is that it is
not really clear
as to what your
hypothesis is,
and what you
want to test. I
typically have
my students
outline the
hypothesis
first, before
defining the
population.You
appear to want
to look at those
how are late
diagnosis
compared to
early. There is
a large
literature on
this which you
should review.
Do a search in
Google Scholar.
You can set up a
study by
identifying
those who come
in late compared
to those who are
early. You need
to define
operationally
what "late" is,
and what "early
is". You could
look at all
women coming in
during a certain
period of time
and do a case
control study.
There are many
different types
of surveys that
you can use, use
something that
has already been
used. You
have to define
your questions
first as to what
factors might be
associated with
a delay in
coming in, then
this will define
your survey. It
would be good
also if you
contacted people
world wide who
have done
research in the
area. It is an
important area,
but you need to
do a little more
homework as to
how to set up
the design


Q16 by Mohammad Asif Alokozai, March 07, 2014  We have conducted the EPI coverage survey, and analyzed the data, the survey is WHO 30*7 cluster survey and the clusters select using PPS. The none response were calculated to be 20 percent, so we have had 30 clusters in each province with 210 interview to be done for each province, but now some province got lesser number of interview e.g. 159, or 166, 169, so does this data need reweighing during analysis? for finding the proportions of coverage using Stata software so what will be the best command to be used? 
A16 by
Eman Eltahlawy, March 07, 2014 If your cluster , 159 166 , or 169 , we must look for reasons why we are not get all out sample size if they take all children in this cluster and they are less than we planned so u not in need to reweigh but if there is some difficulties like security or refusal may be u must try again to approach this area and get what u missing , but if it is difficult so reweigh this areas only. In cluster sample if the cluster become less than expected in some area you must revise why it become less First if cluster include all children in area and they are few in number as in some villages in the desert so you not need for reweigh Second reasons if there is a refusal to participate or security condition at time of visiting those cluster so you may revisit this cluster to get the rest of target Third if there is a big difficulties to reach those cluster again so you should reweigh those cluster again A16 by Nicolas Padilla, March 07, 2014 First, you should know why the surveys are lesser than expected. Second, in a clustered sampling all people in the cluster should be included, maybe including under 18 years. Comments by Mohammad Asif Alokozai, March 09, 2014
Yes the reason for not
getting the complete number of
interviews in some clusters were
because of less number of
children in these clusters, not
refusal or security. as security
were the problem but we have
recruited the interviewers from
local area who were familiar
with context and local
traditions. for less number of
interviews as total per
province, although the number of
interviews were more; but these
participants were above or lower
in age, of set criteria for the
survey (children of 12 to 23)
months.
so this was the reasons
for lower number of interviews.


Q15 by Dr Rajeev Rao Eashwari, March 02, 2014 
I am a medical doctor in charge of eHealth
services for a province in South Africa. I am
planning to do a province wide teleHealth needs
of rural health practitioners. I am struggling to get a survey tool for teleHealth needs analysis with an aim to have focus group interviews. Please advise 
A15
by
Faina Linkov, March 03, 2014 There was an article published on telehealth needs assessment a few years ago, it can be found here http://web.a.ebscohost.com/abstract?direct=true&profile=ehost&scope=site&authtype=crawler&jrnl=1357633X&AN=24677492&h=VrlKH8xL50jraSO%2bizT4eXaconjF0wc1R4UAiak3ec3i7Ey5pwt4V9EfXTmVdtqAW61ZJk%2bbd2wgPACkeUPc5g%3d%3d&crl=c I wanted to emphasize the fact that it's is important not just to assess the needs but also to keep in minds capabilities of the country for which you are trying to assess the needs. Professionals may say that they need extremely high level of expensive technology, but its important to remember that we need to look at what can be done with even limited technology. 

2013 Questions  
Q1 2013 by Nabil D Sulaiman, May 19, 2013  What is the best sampling frame for a national diabetes prevalence study in the absence of updated GHS sample? 
A1 by Mohamed E. Salem, May 25, 2013
In the absence of General Household Survey (GHS) sample, the most accurate and easy alternative is to use the readily available country geographical information to create your own national representative sample. The country map including its geographical information will be used as the sample frame. Geographical Information System (GIS) applications will help you to divide your map into representative clusters of households. ArcGIS is one of the application that could be used to do this exercise.
Here is a youtube link for ArcGIS tutorial
http://www.youtube.com/watch?
Here is an alternative youtube link (in Arabic)
the sound is not very good
http://www.youtube.com/watch?
The program will enable you to
use your country map as a sample
frame. Using the geographical
information available on the
map, you can select the clusters
of households. Within each
cluster you can draw a
systematic random sample using
walk through method inside the
selected study areas.
A1 by Nabil D Sulaiman, May 26, 2013 Various sampling approaches could be explored to seek the best possible sampling frame for a rapidly changing expatriate population in the Gulf region, which are, The National Census (GHS), Water and Electricity Register, Telephone register and National ID. Based on representativeness and feasibility, we in UAE have adopted a novel sampling methodology, which involved systematic random sampling through Preventive Medicine Departments (PMDs), where all expatriate adults in the UAE are legally required to attend every 23 years to renew their residency visa. The PMD is a single place where recruiters, interviewers, nurses and phlebotomists are available. All staff working were nominated and trained for the study. Blood samples for both the study and the visa renewal, were collected at the same visit. 

Q2 by Abdelrahim Mutwakel Gaffar, May 19, 2013  I am
conducting an evaluation study for a project
using "a pre intervention  post intervention"
design. What is the best statistical test to examine the change due to the intervention. 
A2
by Sami AR ALDubai, June 6, 2013 Someone can use SPSS. The statistical test depends on the type of the dependent variable someone want to test. If the dependent variable is normally distributed then you can use ''paired sample TTest''. If it is not normally distributed, then you can use the alternative nonparametric test '' 2 related samples'' (Wilcoxon Signed Ranks). A2 by Shacara Johnson, June 5, 2013 This research would be considered a repeated measures study design or paired design, in which you are interested in observing an intervention change in the same group of subjects. The statistical test to use is called a paired ttest so that you can determine whether a difference exist (finding the mean and standard deviation of the differences between the before and after measurements) and then the tdistribution for the single mean is used to analyze the difference (at the significance level). A2 by Mohammad Babaeeian moghaddam, June 5, 2013 If If we have a repeated measures design with prepost measure and the variables are distributed normally (As assessed by SPSS, we can use a paired t test analysis. If the data are not distributed normally, we can use a Wilcoxson nonparametric test. These two tests can be found in all standard statistical testing procedures (SPSS, SAS and others). A2 by Nicolas Padilla, June 6, 2013 If the variable is quantitative, the mean of differences (measure 1  measure2) then the mean of differences and then t Student (short sample size less than 50) or Z(sample size more than 50). A2 by Rami H. AL Rifai, June 9, 2013 The idea is that "Tell what the type of the dependent variable you have to tell you what type of test you could use". There are 2 main types of variables: 1 Continuous like measuring blood pressure. 2 Discreet: like Yes or No variables. Those variables could be dichotomous (two subcategory) or dichotomous (three subcategories) or even more than three subcategories. However, in pre post intervention studies, the testes to be used if your intervention was carried on the same groups are different from those if your intervention was carried out on different groups like control and intervention groups. For example, if your dependent variable is continuous, and your intervention was on the same group, you have to use Paired Ttest to detect if there was a difference due to intervention or not. But before that you have test the assumption of normality distribution for the dependent variable otherwise you have to use the nonparametric test. A2 by Jay M. Fleisher, June 10, 2013 If your data is continuous and Normally distributed you can use a paired ttest Procedure. This would apply if you can create an index over all questions. If you data is Categorical you can use McNeamars Test. This would be applicable if you are looking at individual questions Remember your data are pared. A2 by Mohamed E. Salem, June13, 2013 If you want to measure the impact of an intervention, the simplest test are 1) The paired sample Ttest; in case your indicator is measured quantitatively (blood sugar level, BMI, etc..). See this link on how to perform paired sample Ttest using SPSS http://www.youtube.com/watch?v=MJGk2sg4EZU 2) the McNemar test; If your indicator is measured qualitatively (diseased or not, complicated or not, etc…) See this link on how to use McNemar http://www.youtube.com/watch?v=k4kqp9S8WEw My suggestion to you is to improve your study design (prepost) intervention design is a weak design if you want to relate the change (improvement) to your intervention. Including a control group will give more strength to your results. Random assignment of the cases and controls to your intervention will make your study even stronger and blindness will be perfect if it is applicable. I am attaching a link to study designs http://www.socialresearchmethods.net/kb/destypes.php In case you operate one of the above designs the analysis should be more indepth using, double difference analysis, regression model and nonequivalent group design in case of quasiexperimental designs 

Q3 by Saad Tai, June 2, 2013 
I am interested to conduct a KAP study on HIV in Pakistan among medical doctors. My question is from where I can get questionnaire or how can I make self made questionnaire. 
A3
by Deena Alasfoor, June 7, 2013 Guideline on how to do a KAP study is on the following link: http://whqlibdoc.who.int/ The research questions depend on the context and how you want to use the information; in general; It is important that each knowledge question is followed up with an attitude and a practice question that helps you in the course of action/intervention . As a researcher you need to identify your questions, based on the context and use the KAP method to explore these. I hope this is helpful. A3 by Bruce G. Weniger, June 8, 2013 Search the medical literature for wellwritten, highquality reports in competitive journals for studies with similar research questions and methods you wish to employ. Many journals are already making available questionnaires, protocols, and other studyrelated documents by optional online download of “supplementary” material for published “printed” reports. For example, the supplementary material to this study (http://dx.doi.org/10.1056/ If the questionnaire is not thus posted, then you can email or write to the paper’s author(s), explaining that you would like to perform a similar study in your own population, using similar questionnaire for comparability. Ask if the author(s) will provide you the questionnaire to adapt for your own study. Offer to acknowledge their assistance in your future paper, and to cite their work if relevant to what you eventually perform and find. A3 by Shacara Johnson, June 8, 2013 You can access information on KAP (Knowledge, Attitudes, and Practice) survey instruments using the World Health Organization’s website or conduct an internet search for HIV KAP surveys in Pakistan. You might also want to search publications by fellow researchers who conducted similar research among HIV care providers in Pakistan and contact them about collaborating or asking for permission to utilize their instrument for your work.
There are several references to HIV KAP
instruments pertaining to the Eastern
Mediterranean region (which would include
Pakistan) stemming from topics ranging from
conducting behavioral surveillance of risk
factors to countrylevel results of KAP
implementation. If you cannot identify a current
instrument being used in Pakistan, then you
might seek to search for other KAP instruments
used in a similar setting for which you can
modify for what you desire to examine in
Pakistan among health care providers. Two
sources as examples from the WHO site that may
be of interest to provide points of
consideration while constructing your instrument
include: http://applications.emro.who. 

Q4 by Murtada Osman, June 11, 2013  How to select the journal for publication? 
A4
by Deena Alasfoor, June 14, 2013 Selecting a suitable journal for publication is one of the most difficult tasks of researchers. The impact factor; interest of the journal and the value of your manuscript; as well as your experience in publishing all count for this. Obviously, you would want to aim at the journals with the highest impact factors. However, it is very hard to publish in these unless your manuscript is of great importance; and you have collaborators who have published in that area earlier. First, select the journals that might interest you; probably these will be the ones you refer to them. If your publication is context free; then you might have a better chance in publishing in an international high impact factor. If your manuscript for example presents national survey results you may want to go to a national or regional journal. Once you have read the authors guide carefully, be sure that your paper matches the journals subjects of interest; then if you have a number of these you could try for the highest impact factor first, and then if rejected go to the lower one until your paper is accepted. This could happen at the first time; but could also take some attempts before getting a journal that accepts your publication. Sometimes the topic had been discussed enough, and the authors do not see that your publication adds a new thing to the existing knowledge, do not get disappointed, keep trying. Good Luck A4 by Eugene Shubnikov, June 11, 2013 I will recommend you to study Supercourse lecture http://www.pitt.edu/~ 

Q5
by
Hanan Abdulghafur Khalil (thought face book), June 23, 2013 
May I ask about the required sample size for pilot study and pretesting and whether the results should be mentioned briefly after the study completed? 
A5 by Eman
Eltahlawy (thought face book), June 23. 2013 Thanks Dr Hanan for your question. It depends on your needs  to test the language of questionnaire, the methodology and logistics inside the field and to ensure that time needed for questionnaire.
A5 by Eugene Shubnikov, June 23. 2013 Dear Hanan, I recommend you to study lectures from Introductory page http://ssc.bibalex.org/helpdesk/introduction.jsf, especially "Sample size and Statistical power Lecture". Thank you for Question! A5 by Fatma Hassan, June 23, 2013 (Facebook) Baker (1994) found that a sample size of 1020% of the sample size for the actual study is a reasonable number of participants to consider enrolling in a pilot study. Another rule of the thumb is to take 30 patients or greater to estimate a parameter (Browne, 1999). Yes the results of pilot should be reported, better in the methodology section. The details of any modifications in the questionnaire based on pilot should be reported. A5 by Nicolas Padilla , June 23, 2013 (Facebook) In a pilot study you need about 1020% of the sample size needed for the larger study A5 by Jay Fleisher, June 23, 2013 (Facebook) Sample Size calculations basically deal with the difference you expect to see and the probability you wish this difference will occur ( Alpha). There are many Sample Size calculators of the Web for free. 

Q6
by
Andrey Kuznetzov (thought face book), July 08, 2013 
Is there any standard R function for calculation of a variance of probability distribution (not sample variance)? Thanks in advance. 
A6 by Jay Fleisher,
July 21, 2013 I think the question pertains to the software package R. There are many distributions besides the Normal Distribution. I think the question is how to find the variance using R of a certain probability distribution. I attach a brief description of what I think this question means.


Q7 by Mohammad Babaeeian moghaddam, July 19, 2013  Animal bites are an important problem in my city and I want to investigate that. How can I design the study (what study design I can use)? Any questionnaires are available for such studies? 
A7 by Nicolas
Padilla,
July 20, 2013 (Facebook) First, are you meaning animals as dogs, for example? If you want to know the burden of animals bites it is better to use a crosssectional design, if you want to know the risk factors for animals bites, it is better to use casescontrols design. 

Q8 by Shatabdi Goon, August 28,2013  If I lost my data from survey, which was used in SPSS program, how I will be able to find out the statistical analysis without having those data(want to evaluate p value). Is it possible to get the p value from the direct result? 
A8 by Nicolas
Padilla, August 29, 2013 You can use epidat (statistical software for free from Xunta de Galicia and PAHO) using tabulated data, for example. A8 by Eman Eltahlawy, September 4, 2013 You can use Epicalac 2000 for tabulated data to evaluate the p value , this easy program and free in the net A8 by Mohamed E. Salem, September 5, 2013 You can use spss and organise ur data for 2*2 table as 0 1, 1 1, 0 0, 1 0 and put the count for each category as a third column . Then go to data weight and weight your data by the count column 

Q9 by Nagah Selim, September 23,2013 

A9 by
Javier Muñiz, September 23, 2013 1. Your study aims at estimating a proportion in the population. 2. You have to consider: a. How do I select the participants?: Sampling procedure b. How many participants should I select: Sample size (related to “a” to some extent). 3. Assuming simple random sampling in “a”, the sample size depends on: a. Size of the population to which you want to infere the proportion that you will find in your study (sample). Surprisingly, it is not very important (unless very small populations). b. Any idea of what you expect to find? (48%, 38% and 47% in your case). 50% is the most demanding assumption (the one that will result in a bigger sample size). Use 50% and you will be safe (your prestudy estimate is very close to 50%). c. What precision do I need? Or, how wide do I want the confidence interval of my estimate? A wide confidence interval is less precise than a narrow one. The narrower the confidence interval desired when presenting the results (better precision), the bigger the sample size. Below find an output of a program that I use (EPIDAT, developed by Xunta de Galicia, Spain and O.P.S.) Sample size and precision to estimate a population proportion Size of the population: 20000 Expected proportion: 50,0% Confidence level: 95,0% Study design: 1,0 Precisión (%) Tamaño de muestra   1,000 6489 2,000 2144 3,000 1014 4,000 583 5,000 377 6,000 264 7,000 195 8,000 149 9,000 118 10,000 96 What does this mean? For example, if you choose to aim at a precision of 2% (IT IS YOUR DECISION AS INVESTIGATOR) for the whole study, you will aim to include 2144 participants. At the end of the study you will be able to say: The prevalence of depression among school children is 50%, with a 95% confidence interval of 4852% (maybe it is not exactly 50%, but you will be pretty sure that the proportion in the population is somewhere between 48% and 52%). When considering subgroups, your precision will decrease because of smaller sample sizes available (for example, you may have around 1000 boys and 1000 girls and the corresponding precision in these subgroups will be around 3%). NOTE: We have assumed simple random sampling (not always feasible when studying kids in schools). If other design is chosen this may affect the sample size (bigger samples will be needed, at least in theory). It is plenty of free programs available to compute the sample size for different study designs. I recommend you EPIDAT 3.1 because it also have some other very useful procedure for tabulated data (http://www.sergas.es/ A9 by Abu Zar, September 23, 2013


Q10 by Nagah Selim, September 23,2013 
If I would like to study prevalence of a disease
among clients attending phcc and I have a rough
estimate on the monthly attendees, can I use
this number as total population for calculating
the sample size?

A10 by
Jay Fleisher, September
23, 2013 If we assume alpha=0.05 and a margin of error = 5% the following sample sizes are For a prevalence of 48%, n=384 38%, n=363 43%, n=377 This is for an unstratified analysis because we don't have info for a difference for males vs females... One should add in about 20% for nonresponders, if applicable I have added a link ( see attachment) that explains how to do it and calculates the sample size for you. One can alternate alpha, size of the margin of error to get different estimates... As for the second question, if I understand it, the answer is no one can't assume it is the whole population. What you have is a sample that goes to pcc. Thus the inference will be to the clinic See a link: http://www.polarismr.com/researchlifeline/samplesizecalculator/ 

Q11 by Naresh Chauhan September 29,2013  What is the sampling technique to draw samples from urban slum to know their behaviour on particular health problems and service utilization? 
A11 by
Jay Fleisher, October
06, 2013 The following steps should be taken to insure an unbiased sampling: 1. Define the Population you want to sample. The inference of any analysis will go to this population 2. Define your basic Measure of Effect. Are you going to sample Homes, Individuals, etc 3. When step 1 and 2 are completed RANDOMLY sample. 4. Conduct Analysis 

Q12 by Mary Mwangome, October 02,2013 
I
am planning to analyse a cohort database for the
effect of half dose of drug x prophylaxis on
deaths. Drug x is a prophylactic medication. 
A12 by
Jay Fleisher, October
06, 2013 There are sampling issues in this study design but I don’t think their fatal. If I understand the design, you have a situation where the patients act as their own controls with respect to dosage. Thus you have paired data. I would break the paring and run separate analyses on each dose. I would try Logistic regression on each dose. This would control for any covariates you have. In other words you can use mortality as your outcome variable and dose1 + covariates for dose 1 for your Independent variables and do the same analysis separately for dose 2. Then compare the odds ratios for each dose along with 95% Confidence Intervals and p values that the Logistic regression will provide to you. If the Confidence Intervals overlap then Dose would have no effect. As for the 30% Lost to followup I think a 70% followup rate is acceptable. STATA, and SAS can do this easily. You would have to report the weaknesses in design of course. The “wash out” period is of concern since there was none. I would give it a try anyway. My opinion is that if your results show a clinically significant difference among the Higher dosage you have an answer. If they do not then you have another answer.
A12 by
Faina Linkov, October
06, 2013
Main points for the answer:
1. Loss to follow up of 30% in 6
years is very good and typical
for studies of this caliber.
2. Survival analysis might
provide good approach for some
of the data analysis.
3. Stata and sas can both do the
analysis.


Q13 by Zafar Fatmi,December 05,2013 
I am trying to analyze the timeseries data for
Air pollution and cardiovascular diseases. I
want to use Generalized Additive Model (GAM) for
analysis. I am unable to find any help in this
regard. I have to adjust for weather variables and age and gender. Please provide some guideline and help. 
A13
by
Faina Linkov, December
14,2013
Perhaps an answer to question 13 is this guideline  

Q14
by
Mohammad Babaeeian moghaddam,December 05, 2013 See Question 7 and Answer 7 first. 
Animal bite(dog bite or petty  home dog) is an important problem in my city and I want investigate causes(factors that make animal angry and then animals attack their owners. How can I design the study(what study design I can use)? Is the questionary available for this study? 
A14
by
Nicolas Padilla, December
6, 2013 You can use a crosssectional design. Search homes with dogs or domestic pets and ask for bites and risk factors (people battered the pet, diseases of the pets etc. Classify the homes in bites by dog or without bites and classify with risk factors or without them and calculate Odds Ratio and Attributable Fraction in exposed. 
