The standard IQ test is intended so that the mean is 100 and the standard deviation is 15 for the population of all adults. We wish to find out the sample size necessary to determine the mean IQ score of statistics students. Assume we want to be 90% confident that our sample mean is in 2 IQ points of the true mean. Suppose then that σ=15 and find out the needed sample size. (Be sure to round correctly!)