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MAT-144 · In-person sections Exam 3 Review · Unit 3
Exam 3 Review · Q18

Mean, median, and mode: computations

Two averages and a counting question. The third part is not “what is the mode” but “how many modes are there” — and zero is a real answer.

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A short walkthrough explaining what you need to know and how to solve this question type lands here once it's recorded.

ALEKS randomizes the numbers each attempt, but the question shape stays the same. Here are three example versions you might see.

No mode at all

Five measurements: 4, 9, 2, 15, 7.

How many modes does this set have? Type 0, 1 or 2.

Two modes

Six values: 7, 7, 12, 12, 15, 20.

How many modes does this set have? Type 0, 1 or 2.

Median and mean

Five values: 4, 9, 2, 15, 7.

What is the median?

Heads up: Your ALEKS version will use different numbers. The numbers in the practice below are different too — that way you're exercising the move, not memorizing one answer.
median: sort, then take the middle even count → average the middle two
mode: the value(s) appearing most often there can be none, one, or several
The mode is the part that surprises people. If one value repeats more than any other there is one mode; if two tie for most frequent there are two; and if every value appears exactly once there is no mode at all. ALEKS gives you a radio button for each case.
Common slips
(1) Assumed there must be exactly one mode. There need not be. (2) Forgot to sort before finding the median. The middle of an unsorted list means nothing. (3) Rounded when the answer was already exact. ALEKS says round to one decimal place if the answer is not an integer — an exact 67.5 stays 67.5.
Sort, average, then count

Each year taxpayers can donate to charity via their tax forms. The following list contains the amounts, in dollars, donated by 8 taxpayers.

41, 88, 62, 88, 55, 73, 29, 88

(a) What is the median? (b) What is the mean? (c) How many modes does the set have, and what are their values?

If an answer is not an integer, round it to one decimal place.

Step 1

(a) The median

Sorted, the list is 29, 41, 55, 62, 73, 88, 88, 88. With 8 values, average the 4th and 5th.
Step 2

(b) The mean

Add all eight and divide by 8.
Step 3

(c) How many modes?

88 appears three times. Every other value appears once. How many modes does the set have?