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Chapter 1: Q 1.57. (page 23)
Ideally, in stratified sampling, the members of each stratum should be relative to the characteristic under consideration.
Ideally, in stratified sampling, the members of each stratum should be homogenous to the characteristic under consideration.
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In Exercises 1.17-1.22, state whether the investigation in question is an observational study or a designed experiment. Justify your answer in each case.
Sex, Sleep, and PTSD. In the article, "One's Sex, Sleep, and Posttraumatic Stress Disorder" (Biology of Sex Differences, Vol. 3, No. 29, pp. 1-7), I. Kobayashi et al. study the relationship between one's sex, sleep patterns, and posttraumatic stress disorder (PTSD) after trauma exposure. The authors report that women have a higher lifetime prevalence of PTSD as well as a greater risk of developing PTSD following trauma exposure. Relationships between sleep and physical health have been documented in a number of studies, and the authors explore the possibility that disruptive sleep habits are common among people with PTSD and also a possible risk factor for the development of PTSD. A questionnaire of men and women with and without PTSD produced data on their sleep habits.
Peanut Allergies. In the article " Food Allergy Advice May Be Peanuts " (Science News, Vol . 174, No. 12, pp . 8-9), N. Seppa reports that early exposure to peanuts seems to lessen the risk of nut allergy. Of 4000 Jewish children sampled in Britain, 1.85 % had peanut allergies; and of 4600 Jewish children sampled in Israel, where early peanut consumption is more common, 0.17 % had peanut allergies. The researcher chose Jewish children in both countries to limit genetic differences between groups.
(a) Is this study descriptive or inferential?
(b) Is this study observational or experimental?
Quick Vote. TalkBack Live, a production of CNN, conducted on-line surveys on various issues. One survey, called a QuickVote, of 680 people asked "Would you vote for a third-party candidate?" Of the 680 people surveyed, 608 ( 89.4 % ) responded "yes" and 72 ( 10.6 % ) responded "no." Beneath the vote tally, the following statement regarding the sampling procedure was found:
This QuickVote is not scientific and reflects the opinions of only those Internet users who have chosen to participate. The results cannot be assumed to represent the opinions of Internet users in general, nor the public as a whole. The Quick Vote sponsor is not responsible for content, functionality or the opinions expressed therein.
Discuss the preceding statement in light of what you have learned in this chapter.
What are the two major types of statistics? Describe them in detail.
The International 500. In Exercise 1.49 on page 16, you used simple random sampling to obtain a sample of 10 firms from Fortune Magazine's list of "The International 500."
(a) Use systematic random sampling to accomplish that same task.
(b) Which method is easier: simple random sampling or systematic random sampling?
(c) Does it seem reasonable to use systematic random sampling to obtain a representative sample? Explain your answer.
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