A science teacher gives a test with 15 questions. This teacher is a hard grader.

Question

The teacher assigns points in the following manner: a correct answer = +1 point, an incorrect answer = -1 point, no answer = 0 points.

So scores on the test could range from +15 to -15. The teacher’s assistant calculates the standard deviation for scores on the test and reports SD = -2.3.

What do we know?

a. The standard deviation was calculated incorrectly.
b. Most students received negative scores.
c. Most students scored below the mean.
d. There is an outlier that has a negative value close to -15.

Answer 1

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