Lightbulbs of a certain type are advertised as having an average lifetime of 750 hours....

Lightbulbs of a certain type are advertised as having an average lifetime of 750 hours. The price of these bulbs is very favorable, so a potential customer has decided to go ahead with a purchase arrangement unless it can be conclusively demonstrated that the true average lifetime is smaller than what is advertised. A random sample of 50 bulbs was selected, the lifetime of each bulb determined, and the appropriate hypotheses were tested using Minitab, resulting in the accompanying output.

What conclusion would be appropriate for a significance level of .05? A significance level of .01? What significance level and conclusion would you recommend?