Question

A statistics professor is at a supermarket waiting in line to buy some groceries. While waiting for the line to move he listened to several people complaining about the long delays. From the different conversions going on he quickly gathers some inform and estimates from the large sample that the mean waiting time is about 12 minutes. He then estimates the population standard deviation to be 1.5 minutes.
1. Let’s assume now that the professor finished his computation and determined that the 90% confidence interval will be within (8.7 – 15.3) minutes. (a) If he now wants a 95% confidence interval, will the range be bigger or smaller than (8.7 – 15.3) minutes?Explain.
2. It is normal to think that more is better. In the question from part (3) (a) Is the 95% confidence interval better than the 90% interval? Explain. (b) If that is the case why do we not use a 100% confidence interval? Explain.

Answer 1