The average length of time required for students to complete a test in an Introductory Statistics course is found to be 65 minutes with a standard deviation of 7 minutes. The time required to complete the test follows a Normal distribution.If students are allowed 80 minutes to complete the test, approximately what percentage of the students will have sufficient time to complete the test?If 20 students are selected at random, what is the probability that at least 13 of them will have sufficient time to complete the test?
The instructor would like to marginally increase the difficulty level of the test by increasing the standard deviation so that 95% of the students have sufficient time to complete the test.
What does the increased standard deviation have to be?