## Practice Problems: Measures of Central Tendency - Answer

Midterm exam scores for a small advanced neuroanatomy class are provided below. Scores represent percent of items marked correct on the exam.

 Data Array 87 99 99 94 75 93 87 88 94 87 75 87 35 87 88 75 87 75 93 35

## Mean

 Mean = X / N = 820 / 10 = 82

## Median

 35 75 75 87 87 87 88 93 94 99

The median is 87. Half of the scores fall above this number and half fall below.

## Mode

Mode is equal to 87. It occurs 3 times; all other scores occur only 2 times or less

## What does this information tell you about students' performance on the midterm (the traditional grading scale is used)?

The mean grade on the midterm was an 82 (a low B). Half of the students had a test score above 87 (a high B or an A). Half the students' scores were lower than an 87. The most common test score was an 87 (a high B).

## Is this data skewed?

Yes, this data is skewed (a negative skew). The score of 35 is an extreme score (outlier), has caused the skew, and distorts the mean.

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