Statistics in a Modern World 800
Solutions to Exam 1

1.  
   1. (iii) census: The number of all vehicle chases is reported.
   2. (i) 2315: 1945 is 16% less than what number? In other words, it is 84% of what number? 1945/.84=2315
   3. (i) year is explanatory (police chases is response)
2.  
   1. (ii) experiment: time of going to bed is imposed by researchers
   2. (i) time of going to bed is thought to explain how "good" sleep is
   3. (ii) categorical: takes values early or late
   4. (iv) daytime wakefulness is how researchers determine how "good" sleep is
   5. (i) quantitative: "The early-to-bed group scored low on test of daytime wakefulness..." tells us that it is assigned a number value.
   6. (iv) magnitude of differences is not specified, we only know they scored "low".
   7. (ii) assignment to treatment groups must be random; original selection of participants for the study seldom is random, but this is OK.
   8. (iii) single blind: researchers wouldn't be told who was in what group, but subjects would certainly have an idea of whether they were sent to bed at 10:30 pm or 2:15 am.
   9. (iv) lack of ecological validity is of most concern because of the artificial setting, much like our jet lag study.
   10. (iii) The fact that researchers only looked at men aged 18 to 25 suggests that both gender and age may play a role in how time of going to bed affects quality of sleep.
3.  
   1. (i) teenagers is the intended population (none of the other choices are general enough)
   2.  
      1. response
      2. response
      3. explanatory
      4. response
   3. (i) extraneous differences between high schools that did and did not provide condoms
   4. (iii) rephrases the statement in the first paragraph
4.  
   1. (i) invalid: it would report the number who admit having a STD, rather than the number who actually have one, which could be quite different.
   2. (ii) reliable, so changes could be noted from year to year
5.  
   1. (ii) Late sleep=good sleep has a sample size of only 8
   2. (iii) the responses of interest are rather sensitive issues
6.  
   1. See paragraph 7: top number dropped 5, bottom number dropped 2, to 148 over 82
   2. (vi) paragraph 6 provides a chemical explanation [I gave 3 points to people who thought it was paragraph 7.]
   3. (ii) See paragraph 2.
7.  
   1. American Journal of Clinical Nutrition
   2. 65 dieters and 62 others
   3. Enola or ordinary vegetable oil used
   4. weight and fat (lost)
   5. 50% more than 10 equals 15 lbs.
8. (c) type of oil used would probably not be detected, but subjects would know if they were sent to bed 4 hours later, or if they were eating dark or white chocolate.

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