Chapter 1: Q 1.29. (page 15)
In sampling, explain why obtaining a representative sample is important.
A representative sample is important to reflect as closely as possible the relevant attributes of the entire population under study.
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In Exercises 1.7-1.12, classify each of the studies as either descriptive or inferential. Explain your answers.
Dow Jones Industrial Averages. From the Stock Performance Guide, published online by Istockl on the website 1Stock1.com, we found the closing values of the Dow Jones Industrial Averages as of the end of December for the years 2004 through 2013.
Number of Farms.The National Agricultural Statistics Service (NASS) conducts studies of the number of acres devoted to farms in each county of the United States. Suppose that we divide the United States into the four census regions (Northeast, North Central, South, and West), take a simple random sample of counties from each of the four regions, and combine all four simple random samples into one sample. What type of sampling design have we used? Explain your answer.
Fill in the following blank:
Observational studies can reveal only association, whereas experiments can help establish .
Lifetimes of Flashlight Batteries.Two different options are under consideration for comparing the lifetimes of four brands of flashlight battery, using 20 flashlights.
(a) One option is to randomly divide 20 flashlights into four groups of 5 flashlights each and then randomly assign each group to use a different brand of battery. Would this statistical design be a completely randomized design or a randomized block design? Explain your answer.
(b) Another option is to use 20 flashlights - five different brands of 4 flashlights-each and randomly assign the 4 flashlights of each sign be a completely randomized design or a randomized block design? Explain your answer.
The members of a population are numbered 1-90.
(a). Use Table I in Appendix A to obtain SRS of size 5 from the population. Start at the two-digit number in line number 15 and column numbers 25-26, read down the column, up the next, and so on.
(b). If you have access to a random-number generator, use it to solve part (a).
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