Ascience teacher gives a test with 15 questions. this teacher is a hard grader. 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?
- the standard deviation was calculated incorrectly.
- most students received negative scores.
- most students scored below the mean.
- there is an outlier that has a negative value close to -15.