A survey/quiz is given to 100 people. The survey has 30 questions. The mean number of correct responses is 21, with a standard deviation of 4. The data is approximately normal.

1. Knowing that the data is approximately normal, approximately what proportion of respondents had a score between 13 and 25?

1. Approximately what proportion of respondents had a score lower than 16? Greater than 23?

1. What are the mean and standard deviation of the number of incorrect responses? (Give a reason)