The distribution of the amount of money spent by students for textbooks in a semester is approximately normal in shape with a me

Question

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The distribution of the amount of money spent by students for textbooks in a semester is approximately normal in shape with a me

an of $240 and a standard deviation of $25. According to the Standard Deviation Rule, in a semester, almost all (99.7%) of the students spent on textbooks in a semester:_________.

Mathematics

1 answer:

babunello [11.8K] · Answer 1 · 2026-04-08T19:12:16+03:00

The last part of the question is asking;

What was the total amount spent by all (99.7%) students on textbooks in a semester?

Response:

almost all (99.7%) of the students spent between $165 and $315 on textbooks in a semester.

Stepwise clarification:

The standard deviation rule informs that for normally distributed data, approximately 99.7% of observations fall within three standard deviations from the mean.

In this case, we have the given mean as 240, and standard deviation as 25

Thus, calculating three standard deviations below the mean: Mean - 3(standard deviation)

equals 240 - (3 × 25)

yielding 240 - 75 = 165

Now, for three standard deviations above the mean: Mean + 3 (standard deviation) = 240 + (3 × 25)

equals 240 + 75 = 315

Therefore, nearly all (99.7%) of the students spent between $165 and $315 on textbooks in a semester.