The average of freshman college students is = 18.5 years, with a standard deviation = 0.4 years. a. Let x? denote the mean age of a random sample of n = 50 students. Determine the mean and standard deviation of the random variable x?. b. Repeat part (a) with n = 100. The average of freshman college students is = 18.5 years, with a standard deviation = 0.4 years. Solution Mean=18.5 SD=0.4/sqrt(50)=0.056.