Microsoft Office Tutorials and References

In Depth Information

Exhibit 3.10
Frequency distribution of pages viewed

We can see from Exhibit 3.10 that the old website is generally located to the

left (lower values of page views) of the new website. Both distributions appear to

have a
central tendency
; that is, there is a central area that has more frequent val-

ues of page views than the extreme values, either lower or higher. Without precise

calculation, it is likely that the average of the pages viewed will be near the cen-

ter of the distributions. It is also obvious that the average, or mean, pages viewed

for the old web site will be less than the average pages viewed for the new web

site. Additionally, the
variation
, or spread, of the distribution for the new website

is larger than that of the old website: the range of the new values extends from 5 to

21, whereas the range of the old values is 1 to 15.

In preparation for our next form of analysis, descriptive statistics, we need to

deﬁne a number terms:

1. The average, or
mean
, of a set of data is the sum of the observations divided by

the number of observations.

2. A frequency distribution organizes data observations into particular categories

based on the number of observations in a particular category.

3. A frequency distribution with a central tendency is characterized by the

grouping of observations near or about the center of a distribution.

4. A
standard deviation
is the statistical measure of the degree of variation of

observations relative to the mean of all the observations. The calculation of the

standard deviation is the square root of the sum of the squared deviations for

each value in the data from the mean of the distribution, which is then divided

by the number of observations. If we consider the observations collected to

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