Nasrin reads that the average adult should get at least 8 hours of sleep per night. She believes most people she knows get less than this. She asks 5 acquaintances how much they sleep each night and finds that their mean is 6.8 hours. What analysis should she do to find out if the mean for time spent sleeping each night for the population of people she knows is really less than 8? one sample z-test one sample t-test one-sample p-test histogram test