The three main measures of central tendency are mean, median, and mode.
1) The mean, also referred to as the average, can be found by adding together the scores of each exam, and then dividing by the number of exams taken.
Then, dividing 431 by 5, we find that Bob's mean score is 86.2
2) The median of a set of data is the number that is literally in the middle. If we order these five grades from lowest to highest, we can find the median by recording the score that appears third.
83, 83, 87, 88, 90 87 is the median of this set.
3) The mode is the number that appears the most often. A set may have no mode, or it may have more than one. In this case, only the number 83 is repeated in the set and is, therefore, the mode.
Therefore, the median would give Bob the highest score.
Hope this helped!