A shop records the number of returns $x$ on each of 50 days: 0 returns on 10 days, 1 on 25 days, 2 on 10 days and 3 on 5 days. Using these frequencies, what is the expected number of returns a day?

1.2

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1.5

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\frac{11}{5}

Correct answerYour answer

15

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Show the answer and explanation

CorrectNot quiteAnswer A

Correct answer: A

The expectation is the arithmetic mean of the frequency distribution: $\frac{\sum fx}{\sum f}$ .
$\frac{0 + 25 + 20 + 15}{50} = \frac{60}{50} = 1.2$ .

Worth noting

1.5 averages the values 0 to 3 without their frequencies.

Ten questions from Random Variables, Expectation & Variance, at your own pace.

Ten questions from Random Variables, Expectation & Variance, at your own pace.

A shop records the number of returns xxx on each of 50 days: 0 returns on 10 days, 1 on 25 days, 2 on 10 days and 3 on 5 days. Using these frequencies, what is the expected number of returns a day?