n average, healthy young adults dream 90 minutes each night, as inferred from a number of measures, including rapid eye movement (REM) sleep. An investigator wishes to determine whether drinking coffee just before going to sleep affects the amount of dream time using one-sample t test. After drinking a standard amount of coffee, dream time is monitored for each of the 25 healthy young adults in a random sample. Results show a sample mean, X, of 100 minutes and a sample standard deviation, s, of 4 minutes.