Page 21 - Statistics for Dummies

Introduction
interval (such as sample size) and work through formulas, step-by-step calcu-
lations, and examples for the most commonly used confidence intervals.
The hypothesis tests in this part show you how to use your data to test
someone’s claim about one or two population means or proportions, or the
difference between them. (For example, a company claims their packages are
delivered in two days on average — is this true?) You discover how research-
ers (should) go about forming and testing hypotheses and how you can
evaluate their results for accuracy and credibility. You also get detailed step-
by-step directions and examples for carrying out and interpreting the results
of the most commonly used hypothesis tests.
Part V: Statistical Studies and the Hunt
for a Meaningful Relationship
This part gives an overview of surveys, experiments, and observational stud- 5
ies. You find out what these studies do, how they are conducted, what their
limitations are, and how to evaluate them to determine whether you should
believe the results.
You also get all the details on how to examine pairs of numerical variables
and categorical variables to look for relationships; this is the object of a great
number of studies. For pairs of categorical variables, you create two-way tables
and find joint, conditional, and marginal probabilities and distributions. You
check for independence, and if a dependent relationship is found, you describe
the nature of the relationship using probabilities. For numerical variables you
create scatterplots, find and interpret correlation, perform regression analyses,
study the fit of the regression line and the impact of outliers, describe the rela-
tionship using the slope, and use the line to make predictions. All in a day’s work!
Part VI: The Part of Tens
This quick and easy part shares ten ways to be a statistically savvy sleuth
and root out suspicious studies and results, as well as ten surefire ways to
boost your statistics exam score.
Some statistical calculations involve the use of statistical tables, and I provide
quick and easy access to all the tables you need for this book in the appen-
dix. These tables are the Z-table (for the standard normal, also called the
Z-distribution), the t-table (for the t-distribution), and the binomial table (for —
you guessed it — the binomial distribution). Instructions and examples for using
these three tables are provided in their corresponding sections of this book.

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