MP3s Two companies market new batteries targeted at owners of personal music players. DuraTunes claims a mean battery life of 11 hours, while RockReady advertises 12 hours.  a) Explain why you would...

MP3s Two companies market new batteries targeted at owners of personal music players. DuraTunes claims a mean battery life of 11 hours, while RockReady advertises 12 hours.

 a) Explain why you would also like to know the standard deviations of the battery lifespans before deciding which brand to buy.

 b) Suppose those standard deviations are 2 hours for DuraTunes and 1.5 hours for RockReady. You are headed for 8 hours at the beach. Which battery is most likely to last all day? Explain.

 c) If your beach trip is all weekend, and you probably will have the music on for 16 hours, which battery is most likely to last? Explain.