A lightbulb manufacturer advertises that average life for its light bulbs is 900 hours. A random sample of 15 of its light bulbs resulted in following lives in hours.
995

590

510

539

739

917

571

555

916

728

664

693

708

887

849


a. Find out xbar and s for this data set.
b. At 10% significance level, do the data offer evidence that the mean life for company's light bulbs differs from the advertised mean? You might suppose the values for bulb life are normally distributed. Employ the traditional method to make your decision.