Statistics & Probability
posted by Alia .
If X is a normal random variable with mean 11, and if the probability that X is less than 12.10 is .72 , then what is the standard deviation of X?
Please note that the answer for the above is stated as c.2.50. However, my answer comes to 1.89 which is not given as an option and I can't figure out where I'm going wrong so please can anyone help me with this problem.