Question

The lifespan of a manufacturer's lightbulb is normally distributed with a standard deviation of 185 hours. The manufacturer claims that the average lifespan of their lightbulbs is 1500 hours. A sample of 70 lightbulbs finds a sample mean 35 hours higher than the manufacturer's claim. Use a significance level of 5%. Enter your final answers in the boxes below. Show ALL working by uploading your handwritten working for this question to Laulima Dropbox within 15 minutes of completing your exam. Correct answers without working shown will not receive full credit. Note that writing Excel functions does NOT qualify as showing working. a) (3) Test the lightbulb manufacturer's claim versus the alternative that the mean is different from 1500 hours. On your working, draw a diagram to support your conclusion. b) (2) Explain intuitively why your conclusion in (a) may change if you were told the sample size is larger.

Answer 1