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