Suppose you wanted to know whether caffeine reduces sleep. You conduct a simple study on yourself in which you record the number of hours you slept on nights when you’ve had caffeine after 7 p.m. and...

Suppose you wanted to know whether caffeine reduces sleep. You conduct a simple study on yourself in which you record the number of hours you slept on nights when you’ve had caffeine after 7 p.m. and calculate a mean number of sleep hours of 7.25. Suppose that you also know that for all nights when you haven’t had caffeine, you sleep an average of 8.5 hours with a standard deviation of 0.5 hours and that your number of hours slept distribution is a normal distribution. Use the z score transformation and Unit Normal Table procedures discussed in this chapter to determine how likely it is that your mean sleep time with caffeine is a score (based on the proportion in the tail) in your population distribution of mean sleep times without caffeine.