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Chapter 1: Q 1.1. (page 7)
Define the following terms:
(a) Population
(b) Sample
Part (a) Population is defined as the collection of all individuals or items under consideration.
Part (b) A sample is that part of the population from which information is collected.
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Regarding observational studies and designed experiments:
(a) Describe each type of statistical study.
(b) With respect to possible conclusions, what important difference exists between these two types of statistical studies?
In Exercises 1.17-1.22, state whether the investigation in question is an observational study or a designed experiment. Justify your answer each case.
The Salk Vaccine. In the 1940s and early 1950s, the public greatly concerned about polio. In an attempt to prevent this disease, Jonas Salk of the University of Pittsburgh developed a polio vaccine. In a test of the vaccine's efficacy, involving nearly million grade-school children, half of the children received the Salk vaccine; the other half received a placebo, in this case, an injection of salt dissolved in water. Neither the children nor the doctors performing the diagnoses knew which children belonged to which group, but an evaluation center did. The center found that the incidence of polio was far less among the children inoculated with the Salk vaccine. From that information, the researchers concluded that the vaccine would be effective in preventing polio for all U.S. school children; consequently, it was made available for general use.
In sampling, explain why obtaining a representative sample is important.
The members of a population are numbered 1-5.
(a) List the 10 possible samples (without replacement) of size 3 from this population.
(b) SRS of size 3 is taken from the population, what are the chances of selecting 1, 3, and 5? Explain your answer.
(c) Use Table I in Appendix A to obtain an SRS of size 3 from the population. Start at the single-digit number in line number 5 and column number 20, read down the column, up the next, and so on.
Ideally, in stratified sampling, the members of each stratum should be relative to the characteristic under consideration.
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