Data were collected from a typing class with 10 students. The class had an average of 56 words per minute (WPM) with a standard deviation of 7 WPM. The teacher realized that the data from one student who typed 70 WPM was not entered. If this student’s results were included in the data set, what effect would it have on the standard deviation?

The added score, 70 WPM, is 14 WPM above the original mean of 56, so it is higher than average but not extremely far from the class’s scores. Including it raises the mean to about 57.3 WPM and increases the standard deviation from 7 to roughly 8 WPM. That is about the same, perhaps a little larger, so choice D is correct.

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