A broadcasting executive is reviewing the prospects of a new television series. According to his judgment the probability is 2,44% that the show will achieve a rating greater than 75 and the probability is 83,89% that it will achieve a rating below 60.

Let X be a rating score. If the executive is certain that the rating has a normal distribution, determine the mean and standard deviation for this distribution.

4.4. If the 99% confidence interval of a statistical situation that has a normal distribution is 10,91 <_ mean <_ 11,27 and has a standard deviation of 0,73, estimate the sample size and mean