Summary Ch. 1
1. Within the context of social research, the purpose of statistics is to organize, manipulate
and analyze data so that researchers can test their theories and answer their questions.
Along with theory and methodology, statistics are a basic tool by which social scientists
attempt to enhance their understanding of the social world.
2. There are two general classes of statistics. Descriptive statistics are used to summarize
the distribution of a single variable and the relationships between two or more variables.
Inferential statistics provide us with techniques by which we can generalize to
populations from random samples.
3. Two basic guidelines for selecting statistical techniques were presented. Variables may
be either discrete or continuous and may be measured at any of three different levels. At
the nominal level, we can compare category sizes. At the ordinal level, categories and
cases can be ranked with respect to each other. At the interval-ratio level, all
mathematical operations are permitted. Interval-ratio level variables can be either
discrete or continuous. Variables at the nominal or ordinal level are almost always
Summary Ch. 2
1. We considered several different ways of summarizing the distribution of a single variable
and more generally reporting the results of our research. Our emphasis throughout was
on the need to communicate our results clearly and concisely. You will often find that as
you strive to communicate statistical information to others the meanings of the
information will become clearer to you as well.
2. Percentages and proportions, ratios, rates and percentage change represent several
different techniques for enhancing clarity by expressing our results in terms of relative
frequency. Percentages and proportions report the relative occurrence of some category
of a variable compared with the distribution as a whole. Ratios compare two categories
with each other and rates report the actual occurrences of some phenomenon compared
with the number of possible occurrences per some unit of time. Percentage change
shows the relative increase or decrease in a variable over time.
3. Frequency distributions are tables that summarize the entire distribution of some
variable. It is very common to construct these tables for each variable of interest as the
first step in a statistical analysis. Columns for percentages cumulative frequency and/or
cumulative percentages often enhance the readability of frequency distributions.
4. Pie and bar charts, histograms, stem and leaf plots and line charts are graphic devices
used to express the basic information contained in the frequency distribution in a
compact and visually dramatic way.
Summary Ch. 3
1. The three measures of central tendency presented in this chapter share a common
purpose. Each report some information about the most typical or representative value in
a distribution. Appropriate use of these statistics permits the researcher to report
important information about an entire distribution of scores in a single, easily understood
2. The mode reports the most common score and is used most appropriately with
nominally measured v