Praxis Core Prep: How to Measure Arithmetic Mean, Median, or Mode - dummies

Praxis Core Prep: How to Measure Arithmetic Mean, Median, or Mode

By Carla Kirkland, Chan Cleveland

Yes, the Praxis Core will ask you about mean, median, and mode. The measures of central tendency are all types of averages of data sets. When preparing for the Praxis Core exam, you need to be able to decide the value of a data set that best describes the entire data set.

Mastering the mean

For a data set with no high or low numbers, the mean, also known as the average, is the most popular measure of central tendency. To find the mean of a set of values, use the following formula:

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Marking the middle with the median

When the data set has a couple of values higher or lower than the others, the median is the most popular measure of central tendency. When finding the median of a data set, you must first ensure that the data is in order from least to greatest.

Use the crossout method to mark out values until you get to the center. If two values are left in the center, take the average of them.

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Making the most of the mode

When your data set is filled with the same data values, then the mode wins as the most popular value. In the following data set, the mode is 23 because it appears most often.

15, 20, 23, 23, 23, 40, 45, 60

The table below contains Kelsey’s Face Time usage for 1 week (in minutes).

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Find the mean, median, and mode of the data set. Which measure best describes the amount of time spent on Face Time?

  • Mean: ?

  • Median: ?

  • Mode: ?

The mean (93.85) and mode (65) are close to only a few data points; the median (75) is close to most data points, so the best measure of central tendency for this data set is the median. You can say that Kelsey spends an average of 75 minutes per week on Face Time. Here’s how to calculate each of the three measures of central tendency:

Mean = 45 + 65 + 65 + 75 + 77 + 80 + 250 = 657 ÷ 7 = 93.85

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Mode = 65, because it appears most frequently in this set of data.