An automobile battery manufacturer claims that its midgrade battery has a mean life of 50 months with a standard deviation of 6 months. Suppose the
distribution of battery lives of this particular brand is approximately normal.
6a. On the assumption that the manufacturer's claims are true, find the
probability that a randomly selected battery of this type will last less than 48
months.
Your answer
6b. On the same assumption, find the probability that the mean of a random
sample of 36 such batteries will be less than 48 months.
Your answer