Asked by Anonymous

The length of country and western songs is normally distributed and has a mean of 200 seconds and a standard deviation of 30 seconds. Find the probability that a random selection of 9 songs will have mean length of 186.30 seconds or less. Assume the distribution of the lengths of the songs is normal.
Answered by Chol

z = (186.3-200)/(30/sqrt(9))
z = -1.37, you can use your table
Answered by giovanny
The average age of doctors in a certain hospital is 50.0 years old. Suppose the distribution of ages is normal and has a standard deviation of 4.0 years. If 16 doctors are chosen at random for a committee, find the probability that the average age of those doctors is less than 50.3 years. Assume that the variable is normally distributed.
Answered by Feet
Cd
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