1.Suppose the lengths of the pregnancies of a certain animal are approximately normally distributed with mean =289days and standard deviation =15days.

2.Time spent using e-mail per session is normally distributed, with =7 minutes and =2 minutes

c) If you select a random sample of 100 sessions, what is the probability that the sample mean is between 6.8 and 7.2 minutes?

3. Some students paid a private tutor to help them improve their results on a certain mathematical test. These students had a mean change in score of +18 points, with a standard deviation of 62

points. In a random sample of 100 students who pay a private tutor to help them improve their results, what is the likelihood that the change in the sample mean score is less than 10 points?

4.Suppose a simple random sample of size n=49 is obtained from a population with =71 and

=28. (b) What is Px>75.6? (c) What is Px61.6? (d) What is P65.4