How much sleep do high school students get on a typical...

How much sleep do high school students get on a typical school night? An interested student designed a survey to find out. To make data collection easier, the student 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 student obtain? (b) Explain why this sampling method is biased. Is 7.2 hours probably higher or lower than the true average amount of sleep last night for all students at the school? Why?

Transcript

00:03 All right, we want to do a survey to get an idea of how much sleep students get per night.

00:10 So we stood outside the school, and as students walked into school in the morning, we asked them how much sleep they got last night, the night before.

00:22 So the first 100 students were surveyed.

00:26 So these are the very first 100 students walking in the school, and on average, they reported 7 .2 hours of sleep.

00:32 Now, what kind of sampling is this? this is convenience sampling.

00:39 It was convenient to put ourselves in just one location in front of the school building and convenient to just survey the first 100 students walking into the building.

00:51 So this was convenience sampling.

00:56 And convenience sampling typically leads to biased results.

01:02 And here's why.

01:05 We should have conducted a random sample, not a convenience sample.

01:10 A random sample would be where every student in the school has an equal chance of being chosen, maybe put all their names in the hat, select 100 of their names, or assign each student a number, and randomly select 100 of those numbers.

01:25 But this was a convenience sample because it was convenient to just be in one location, instead of trying to give every student in the school an equal chance of being part of the sample, part of the survey.

01:38 It was convenient to just put ourselves in front of the school building and convenient to just ask the first 100 students...

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