A lightbulb manufacturer believes that her compact fluorescent bulbs last longer than incandescent bulbs. She knows that the mean number of hours that a 60-watt incandescent bulb lasts is 2,350 hours, with a standard deviation of 130 hours (these are population values). She gets a random sample of her compact fluorescent bulbs and measures the mean number of hours they last. She is going to use a single-sample z test to compare the sample mean to the population mean.

(a) Should she do a one-tailed test or a two tailed test?

(b) Write the null and alternative hypotheses.