Evidence-Based Practice for Nurses

Measures of central tendency offer another way to describe raw data. These
measures provide information about the “typical” case to be found in the data.
The mean, median, and mode are the three terms most commonly used to describe
the tendency of data to cluster around the middle of the data set (i.e., “averages”
for the data). The mean and median are used to describe continuous-level data,
while the mode is used to describe both continuous- and nominal-level data.
Because the mean and median may be calculated values, they can be rounded
to the nearest number; however, the mode is never rounded because it is an
actual data point.

Mode

The mode is the easiest measure of central tendency to determine because it is
the most frequently occurring value in a data set. It is the highest tally when
counting and is the highest frequency in a distribution table. Modality refers to
the number of modes found in a data distribution. Data can be amodal (without
a mode), unimodal (with one mode), or bimodal (with two modes). There is
no specific term to indicate when data have more than two modes. The mode
does not mean that a data value occurs more than once in a frequency distribu-
tion because the mode is an actual data point. The mode is not affected by the
existence of any extreme values in the data. Table 13-4 demonstrates how the

13.3 Measures of Central

Tendency

At the end of this section, you will be able to:

‹ Describe measures of central tendency and their uses

KEY TERMS

measures of central

tendency: Measures

(e.g., mean, median,

mode) that provide

information about

the typical case

found in the data

mode: The

most frequently

occurring value in a

data set

modality: The

number of modes

found in a data

distribution

amodal: A data set

that does not have

a mode

unimodal: A data

set with one mode,

such as a normal

distribution

bimodal: A data set

with two modes

Data Points Type of Mode Location of Mode

{0, 1, 2, 3} amodal N/A

{0, 1, 2, 2} unimodal 2

{1, 1, 2, 2} bimodal 1 and 2

{1, 1, 1, 2, 2} unimodal 1

{1, 1, 1, 2, 596} unimodal 1

TABLE 13-4 Mode

13.3 Measures of Central Tendency 337