The Handy Math Answer Book

Bar graphsare similar to histograms, but with the columns separated by each other

by small distances. They are commonly used for qualitative variables. A pie chartis

another way to represent data graphically. In this case, it is a circle divided into segments,

or “pie” wedges. Each segment represents not only a certain category, but its proportion

to the total set of data. Another type of graph is the line graph,which is similar to those

seen in geometry: a representation of the data from connected point to connected point.

They are one of the most common graphs seen for simple statistical data collection.

What is a frequency table?

A frequency table is a way of summarizing data. In particular, it is a way of displaying

how entities (such as scores, number of people, etc.) are divided into intervals, and of

counting the number of entities in each interval. The result shows the actual number

of entities, and even the percentage of entities in each interval. For example, if we sur-

vey the number of people working in the 10 offices in a building, the data set might

look like the following:

Number of people working in each office:

3141324112

Another way to present this data is to note how many offices had 1, 2, 3, or 4 peo-
ple working in them. This is known as finding the frequencies of each of the data val-
ues. An example of such a frequency table would be as follows:
number of people 01234
264 frequency 04222

What does the term “statistically significant” mean?

F

or most of us, “significant” means important; in statistics it means probably

true (not due to chance) but not necessarily important. In particular, signifi-

cance levels in statistics show how likely a result is due to chance. The most

common level—one thought to make it good enough to believe—is 0.95, which

means the finding has a 95 percent chance of being true.

This can also be misleading, however. No statistical report will indicate a 95

percent, or 0.95, in its answer, but it will show the number 0.05. Thus, statisti-

cians say the results in a “backward” manner: they say that a finding has a 5 per-

cent chance of not being true. To find the significance level, all one has to do is

subtract the number shown from 1. For example, a value of 0.05 means that

there is a 95 percent (1 .05 0.95) chance of it being true; for a value of 0.01,

there is a 99 percent chance (1 0.01 0.99) of it being true; and so on.