Astudent wants to estimate the mean score of all college students for a particular exam. first use the range rule of thumb to make a rough estimate of the standard deviation of those scores. possible scores range from 300 to 2200. use technology and the estimated standard deviation to determine the sample size corresponding to a 90% confidence level and a margin of error of 100 points. what isn't quite right with this exercise? the range. rule of thumb. estimate for the standard deviation. nothing.