AP Statistics FINAL ch. 7

Suppose we select and SRS of size n = 100 from a large population having proportion of successes. Let p-hat be the proportion of successes in the sample. For which value of p would it be safe to use the Normal approximation to the sampling distribution of p-hat?

0.85

A researcher initially plans to take an SRS of size n from a population that has mean 80 and std dev. 20. If he were to double his sample size (to 2n) , the standard dev. of the sampling distribution of the sample mean would be multiplied by...

1/√2

A study of voting chose 663 registered voters at random shortly after and election. Of these, 72% said they had voted in the election. Election records show that only 56% of registered voters voted in the election. Which of the following statements is true about the boldface numbers?

72% is a statistic and 56% is a parameter.

The number of undergraduates at Johns Hopkins University is approximately 2000 while the number at Ohio State University is approx 40000. At both schools, a simple random sample of about 3% of the undergraduates is taken. Each sample is used to estimate the proportion p of all students at the university who own an iPod. Suppose that, in fact, p = 0.80 at both schools. Which of the following is the best conclusion?

The estimate from John Hopkins has more sampling variability than that from Ohio State

Which of the following statements about the sampling distribution of the sample mean is INCORRECT?

The sampling distribution shows how the sample was distributed around the sample mean.

The student newspaper at a large university asks an SRS of 250 undergraduates, "Do you favor eliminating the carnival from the term-end celebration?" All in all, 150 of the 250 are in favor. Suppose that (unknown to you) 55% of all undergraduates favor eliminating the carnival. If you took a very large number of SRSs of size n =250 form this population, the sampling distribution of the sample proportion p-hat would be...

approximately Normal with mean 0.55 and standard deviation of 0.03

The central limit theorem is important in statistics because it allows us to use the Normal distribution to make inferences concerning the population mean...

if the sample size is reasonably large (for any population).

A machine is designed to fill 16oz bottles of shampoo. When the machine is working properly, the mean amount poured into the bottles is 16.05oz with a standard deviation of 0.1oz. Assume that the machine is working properly. If four bottles are randomly selected each hour and the number of oz in each bottle is measured, then 95% of the observations should occur in which interval?

none of the above

The Gallup Poll has decided to increase the size of its random sample of voters from about 1500 people to about 4000 people right before an election. The poll is designed to estimate the proportion of voters who favor a new law banning smoking in public buildings. The effect of this increase is to...

reduce the variability of the estimate

Suppose that you are a student aide in the library and agree to be paid according to the "random pay" system. Each week, the librarian flips a coin. If the coin comes up heads, your pay for the week is $80. If it comes up tails, your pay is $40. You work in the library for 100 weeks. Suppose we choose an SRS of 2 weeks and calculate your average earnings x-bar. The shape of the sampling distribution of x-bar will be...

symmetric but not normal