1. An inspector inspects large truckloads of potatoes to determine the proportion p with major defects prior to using the potatoes to be made into potato chips. She intends to compute a 95% confidence interval for p. To do so, she selects an SRS of 50 potatoes from the over 2000 potatoes on the truck. Suppose that only 2 of the potatoes sampled are found to have major defects. Which of the following assumptions for inference about a proportion using a confidence interval are violated?
A. The population is at least 10 times as large as the sample.
B. n is so large that both the count of successes n and the count of failures n (1 - ) are 10 or more.
C. There appear to be no violations.
2. An inspector inspects large truckloads of potatoes to determine the proportion p in the shipment with major defects prior to using the potatoes to make potato chips. Unless there is clear evidence that this proportion is less than 0.10 she will reject the shipment. To reach a decision she will test the hypotheses
H0: p = 0.10, Ha: p < 0.10
using the large sample test for a population proportion. To do so, she selects an SRS of 50 potatoes from the over 2000 potatoes on the truck. Then
A. the Normal approximation to the binomial can safely be used for this significance test.
B. the Normal approximation to the binomial should not be used for this significance test.
C. the alternative hypothesis should be Ha: p > 0.10.
3. 100 rats whose mothers were exposed to high levels of tobacco smoke during pregnancy were put through a simple maze. The maze required the rats to make a choice between going left or going right at the outset. 80 of the rats went right when running the maze for the first time. Assume that the 100 rats can be considered an SRS from the population of all rats born to mothers exposed to high levels of tobacco smoke during pregnancy (note that this assumption may or may not be reasonable, but researchers often assume lab rats are representative of large populations since they are often bred to have uniform characteristics). Let p be the proportion of rats in this population that would go right when running the maze for the first time. A 90% confidence interval for p is
A. 0.8 ± 0.040.
B. 0.8 ± 0.066.
C. 0.8 ± 0.078.