Elementary Statistics - Central Limit Theorem Worksheet The average cost of college for one year is $26,489 with a standard deviation of $3204. If 36 colleges are selected at random, find the following probabilities. 1. Find the probability that the sample mean cost for the 36 schools is less than $25,000. 2. Find the probability that the sample mean cost for the 36 schools is more than $26,000. 3. Find the probability that the sample mean cost for the 36 schools is between $24,000 an $26,000