1.) What will jappen to the length of the interval estimate if we have increas the confidence level by 90% to 95% interval?

2.) Suppose that the time alloted for commercials on a primetime TV program is known to have a normal distribution with a stadard deviation of 1.5 minutes. A study of 35 showings gave an average commercial time of 10 minutes. Compute for the maximum error, given a 98% confidence level. Express in 2 decimal places.

3.) An electrical firm manufactures light bulbs that have a length of life that is approximately normally distributed, with a standard deviation of 40hrs. How large a sample is needed if we wish to be 95% confident that our sample mean will be 10hrs of the true mean?