Assume that x is normally distributed random variable with a mean of 30 and a standard deviation of 6 . Find P(x < 30).
Q. 2The grades of an examination whose mean is 82 and whose standard deviation is 14 are normally distributed. Find the grade such that only 1 will score above it.
Q. 3The grades of an examination whose mean is 82 and whose standard deviation is 14 are normally distributed. The top 10 are to receive a special commendation. What score must be surpassed to receive this special commendation?
Q. 4The grades of an examination whose mean is 82 and whose standard deviation is 14 are normally distributed. Anyone who scores below 55 will be retested. What percentage does this represent?
Q. 5The length of life of a certain type of washer is approximately normally distributed with a mean of 6.2 years and a standard deviation of 1.4 years. What period of time should the manufacturer give as a guarantee if it is willing to replace only 0.5 of the machines?
Q. 6The length of life of a certain type of washer is approximately normally distributed with a mean of 6.2 years and a standard deviation of 1.4 years. If this machine is guaranteed for two years, what is the probability that the machine you purchased will require replacement under guarantee?
Q. 7The waiting time x at a fast-food restaurant during lunch time is approximately normally distributed with a mean of 4.5 min and a standard deviation of 1.2 min. Find the value of the 75th percentile for x.
Q. 8The waiting time x at a fast-food restaurant during lunch time is approximately normally distributed with a mean of 4.5 min and a standard deviation of 1.2 min. Find the probability that a randomly selected customer has to wait more than 6.8 min.
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