Question: The CIA has specialist who analyze the frequencies of letters of the alphabet in an attempt to decipher intercepted messages. In Standard English text, the letter r is used at a rate of 7.7%.

a. Find the mean and the standard deviation for the number of times the letter r will be found on a typical page of 2600 characters. If you use binomial probability distribution formulas, please justify that it is a binomial probability distribution.

a. In an intercepted message sent to Iraq , a page os 2600 characters is found to have the letter r occurring 175 times. Is this unusual?