How should the principal use the 3.2 hours she…

How should the principal use the 3.2 hours she found?

Question 16

MediumOriginal question

A principal wants to know the average daily screen time of the 1,200 students in her school. She picks 60 students by drawing names at random from the full roll and finds that they average 3.2 hours a day.

How should the principal use the 3.2 hours she found?

As the exact mean of all 1,200 studentsCorrect answerYour answerAs an estimate of the school's mean screen timeCorrect answerYour answerAs proof that every student spends 3.2 hoursCorrect answerYour answerNot at all, since 60 is only 5% of the schoolCorrect answerYour answer

Show the answer and explanation

CorrectNot quiteAnswer B

Correct answer: B

A statistic from a random sample estimates the matching parameter.
Another sample would give a slightly different mean, so 3.2 hours is an estimate, not the exact value.

Worth noting

A random sample of 5% can estimate well; what matters is that it is random, not that it is large.

Concept: A statistic estimates a parameter
Typical timeTypical: 120 s
Your timeYours: —

The rule this testsPopulation and sample

Practise this chapter →

Ten questions from Sampling, Inference & the t-Test, at your own pace.

Practise this chapter →

Ten questions from Sampling, Inference & the t-Test, at your own pace.

How should the principal use the 3.2 hours she found?

Question 16

Explanation