Statistics in a Modern World 800
Solutions to Exam 1

1.  
   1. (i) sample survey/observational study (researchers only tested; they imposed no changes)
   2. (iii) type of surface
   3. (ii) bacteria level
   4. (i) funding (see last sentence); an easy way to increase Clorox sales would be to convince people that they need to clean their desks more
   5. (i) unknown; there were apparently many of each of the twelve types of surfaces tested
2.  
   1. (ii) experiment; researchers did impose a treatment, namely the program to help children earn good grades and get along with others
   2. (ii)schoolchildren in high-crime areas (schoolchildren is too general; 350 schoolchildren in high-crime areas comprise the sample, not the population)
   3. (ii) response variable
   4. (i) explanatory variable
   5. (i) categorical variable
   6. (ii) discrete measurement variable
   7. yes, since specific choices were provided
   8.  
      1. University of Washington Social Development Research Group
      2. 350 students (and their parents and teachers) in 18 Seattle schools in high-crime areas between 1981 and 1986
      3. A. participants in a program to earn good grades and get along with others; B. non-participants
      4. 38; 56
   9. (iii) about the same---15% or 16%---for both groups
   10. (ii) prospective
   11. (ii) no; students would know if they were involved in the program
3. (iii) unreliable measure
4. (iii) desire to please
5. 1. (i) confounding variables
   2. (i) outgoing, high-achieving girls tend to participate in sports, and they also tend to succeed as adults
   3. (iii) make the assignments at random; (ii) large sample is better
6. (iii)experiment
7. (b) children who attended preschool may tend to come from families with a higher income, and thus less likely to commit crimes
8. (ii) apparently no, since the percentages of"yes" and "no" answers add up to 100%

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