When reading articles in which averages are used, nurses must carefully
examine the conclusions drawn. For example, suppose a nursing unit employs
five staff nurses and a nursing manager. Annual salaries of these employees are
$66,500, $66,500, $67,000, $68,000, and $69,000. The nursing manager earns
$133,000. During contract negotiations, nurses indicate that they need a raise.
One individual claims the “average” salary is $67,000 per year (median), while
another says the “average” salary is $66,500 (the mode). When confronted by
the administration, the nurse manager responds by saying the “average” salary
is actually $78,333.33 (mean). So, who is correct? In fact, they are all correct.
They are just using different meanings of average. This example demonstrates
how easy it is to manipulate statistics and why careful attention must be given
to the interpretation of data being presented.
When appraising evidence, it is helpful to remember that the mean is the
best measure of central tendency if there are no extreme values, and the me-
dian is best if there are extreme values. Because they are calculated, the mean
and median are not necessarily actual data values, whereas the mode must be
an exact data point. The mean and median are unique values (again, because
they are calculated), but the mode might be unique or might not exist at all,
or there might be multiple modes. The mean is greatly affected by extreme
values, the median is marginally affected, and the mode is not affected. TheUngrouped Data Grouped DataAge Tally FrequencyCumulative
Frequency Age Tally FrequencyCumulative
Frequency
18 | 3 3 18–19 |||| | 6 6
19 ||| 3 6 20–21 |||| | 6 12
20 | 1 7 22–23 |||| 5 17
21 |||| 5 12 24–25 | 1 18
22 ||| 3 15 > 25 || 2 20
23 || 2 17 Total 20
25 | 1 18
27 | 1 19
28 | 1 20
Total 20TABLE 13-6 Median of Age Data for 20 Subjects
340 CHAPTER 13 What Do the Quantitative Data Mean?