Question

Emi computes the mean and variance for the population data set 87, 46, 90, 78, and 89. She finds the mean is 78. Her steps for finding the variance are shown below.
What is the first error she made in computing the variance?

Emi failed to find the difference of 89 - 78 correctly.

Emi divided by N - 1 instead of N.

Emi evaluated (46 - 78)^2 as -(32)^2.

Emi forgot to take the square root of -135.6.

Answer 1

The error she made is Emi evaluated (46-78)² as - (32)² is wrong.

What is variance?

Variance is calculated as the average of squared differences of the data observations from the mean.

Given data: 87, 46, 90, 78, and 89.

Here, the first Emi find the difference of 89 - 78 correctly.

Now, Emi division is also correct.

Now, Emi evaluated (46 - 78)^2 as -(32)^2 is wrong.

(46-78)² = (-32)²

Here she used the negative sign outside.

Hence, Emi evaluated (46 - 78)^2 as -(32)^2 is wrong.

Learn more about this concept here:

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