Asimple random sample (srs) of 100 of a certain popular car in 1997 found that 20 had a certain minor defect in the brakes. an srs of 400 of the same car in 1998 found that 50 had the minor defect in the brakes. let p1 and p2 be the proportion of all cars of this model in 1997 and 1998, respectively, that contained the defect. a 90% confidence interval for p1−p2 is:

Recall that the owner of a local health food store recently started a new ad campaign to attract more business and wants to know if average daily sales have increased. historically average daily sales were approximately $2,700. the upper bound of the 95% range of likely sample means for this one-sided test is approximately $2,843.44. if the owner took a random sample of forty-five days and found that daily average sales were now $2,984, what can she conclude at the 95% confidence level?