econ

answer these three questions. 2pages

1. The quality control manager at a lightbulb factory needs to estimate the mean life of a new type of lightbulb. The population standard deviation is assumed to be 60 hours. A random sample of 30 lightbulbs shows a sample mean life of 450 hours. Construct and explain a 98% confidence interval estimate of the population mean life of the new lightbulb.

2. A survey of first-time home buyers found  that the sample mean annual income was $48,000. Assume that the survey used a sample of 25 first-time home buyers and that the sample standard deviation was $1,150. Compute and explain a 95% confidence interval estimate of the population mean.

3. A telephone poll of 800 American adults asked "where would you rather go in your spare time?"  One response, by 275 adults, was "a movie". Compute and explain a 90% confidence interval estimate of the proportion of all American adults who would respond "a movie".