How much sleep do high school students get on a typical school night? A counselor designed a survey to find out. To make data collection easier, the counselor surveyed the first 100 students to arrive at school on a particular morning. These students reported an average of 7.2 hours of sleep on the previous night.

a. What type of sample did the counselor obtain?

b. Explain why this sampling method is biased. Is 7.2 hours probably greater than or less than the true average amount of sleep last night for all students at the school? Why?