The data file includes the text of three books of the Bible (Joshua, Jonah and Philippians) using the ESV translation. While these are all great books, our only interest for this project is how often each letter is used. 1) In the Word file containing the Biblical text, use the "Find" feature to identify how many times each letter occurs (i.e. the letter's frequency). Excel spreadsheet to display the number of occurrences of each letter in the English alphabet. 2) In the Excel spreadsheet, sum your frequencies to compute the total number of letters in the 3 books (this is n). a) In your spreadsheet, use the formula = to compute the sample proportion of each letter's appearances relative to total number of letters (i.e. find the relative frequency of each letter). Use the Excel sorting function to sort the letters in order of their frequencies. b) Use the simple Confidence Interval (CI) formula (2.576 ,+ 2.576 ) to find a 99% CI on the proportion of how often each letter is used in English text in general. Enter the lower bound in the first Excel column using the formula 2.576 and the upper bound in the next column using the formula +2.576 .

3) Identify those letters whose Cls do not overlap with any the CIs of any of the other letters. (For example the CI [0.042, 0.052] overlaps with [0.050, 0.060] because the upper bound of the first CI is greater than the lower bound of the second CI.) List the letters with the non- overlapping Cis and specify how many such letters there are. 4) The previous analysis could be useful if our goal was to decipher an encrypted message, where each letter is scrambled (for example, each "a" might become a "g", while each "b" might become an "o" and so forth). a) Assume that the letter "z" in encrypted message has a relative frequency of 0.08 (it accounts for 8% of the total number of letters). Which letter's Confidence Intervals (from question 2) contain 0.08 and thus are the most likely candidates to be the letter which was encrypted as "z"? b) Further assume that "y" in the encrypted message has a relative frequency of 0.025 (2.5%). Which letter's CIs, computed in question 2, contain 0.025? c) If "x" in the encrypted message has a relative frequency of 0.015 (1.5%), which letter's question 2 CIs contain 0.015? 5) a) How many possible ways are there to assign the actual letters of the alphabet to the encrypted letters in a message? (Hint: "A" could be assigned to any one of the 26 letters, including itself. Once "A" has been assigned, "B" can be assigned to any letter except the letter that corresponds to "A"). b) As your answer to part (a) makes clear, there are a super-high number of possible ways all the letters could be assigned. Knowing something about each letter's relative frequency dramatically reduces the number of likely combinations. For example, if there were only 3 possible options for half of the encrypted letters (i.e. 13 letters) in the message and only 2 possible options for the remaining 13 letters, then how many possible ways would there be to assign real letters to the letter in the encrypted message?