A manufacturer of flashlight batteries took a sample of 15 batteries from a day's production and used themcontinuously until they failed to work. The life lengths of the batteries, in hours, until they failed.

At the .05 level of significance, is there evidence to suggest that the mean life length of the batteries produced by this manufacturer is more than 500 hours?

See attached Excel for Data.

426
317
545
264
1049
631
512
366
592
562
298
421
678
345
987