Quiz 8.1A AP Statistics

A consumer watchdog organization estimates the mean weight of 1-ounce ―Fun-Size‖ candy bars to see if customers are getting full value for their money. A random sample of 25 bars is selected and weighed, and the organization reports that a 90% confidence interval for the true mean weight of the candy bars is 0.992 to 0.998 ounces. (a) What is the point estimate from this sample? (b) What is the margin of error? (c) Interpret the 90% confidence interval 0.992 to 0.998 in the context of the problem. (d) Interpret the confidence level of 90% in the context of the problem. 360 The Practice of Statistics, 4/e- Chapter 8 © 2011 BFW Publishers 2. A manufacturer of flashlights wants to know how well one of their newer styles is selling in a chain of large home-improvement stores. They select a simple random sample of 20 stores, record how many of the flashlights were sold in a 30-day period, and construct a 95% confidence interval for the mean number of flashlights sold. (a) Discuss whether this study meets the necessary conditions for constructing a confidence interval. If you think one of the conditions has not been met, what additional information would be required or what change in the study would you recommend? (b) If, instead of constructing a 95% confidence interval, the flashlight manufacturer constructed a 98% confidence interval, would the 98% interval be wider, narrower, or the same width as the 95% interval? Explain. (c) How would the width of confidence interval change if the flashlight manufacturer took a larger sample? Explain. © 2011 BFW Publishers The Practice of Statistics, 4/e- Chapter 8 361 Quiz 8.1B AP Statistics Name: 1. Crop researchers are interested in the productivity of a new variety of corn. They plant 25 plots with randomly-selected seeds of the new variety, record the yield in bushels per acre, and find that a 99% confidence interval for the true mean yield is 118 to 130 bushels per acre. (a) What is the point estimate from this sample? (b) What is the margin of error? (c) Interpret the 99% confidence interval 118 to 130 in the context of the problem. (d) Interpret the confidence level of 99% in the context of the problem