Page 20 - Statistics for Dummies

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Statistics For Dummies, 2nd Edition
Part II: Number-Crunching Basics
This part helps you become more familiar and comfortable with making,
interpreting, and evaluating data displays (otherwise known as charts,
graphs, and so on) for different types of data. You also find out how to sum-
marize and explore data by calculating and combining some commonly used
statistics as well as some statistics you may not know about yet.
Part III: Distributions and
the Central Limit Theorem
In this part, you get into all the details of the three most common statistical
distributions: the binomial distribution, the normal (and standard normal,
also known as Z-distribution), and the t-distribution. You discover the charac-
teristics of each distribution and how to find and interpret probabilities, per-
centiles, means, and standard deviations. You also find measures of relative
standing (like percentiles).
Finally, you discover how statisticians measure variability from sample to
sample and why a measure of precision in your sample results is so important.
And you get the lowdown on what some statisticians describe as the “Crowning
Jewel of all Statistics”: the Central Limit Theorem (CLT). I don’t use quite this
level of flourishing language to describe the CLT; I just tell my students it’s an
MDR (“Mighty Deep Result”; coined by my PhD adviser). As for how my stu-
dents describe their feelings about the CLT, I’ll leave that to your imagination.
Part IV: Guesstimating and
Hypothesizing with Confidence
This part focuses on the two methods for taking the results from a sample
and generalizing them to make conclusions about an entire population.
(Statisticians call this process statistical inference.) These two methods are
confidence intervals and hypothesis tests.
In this part, you use confidence intervals to come up with good estimates for
one or two population means or proportions, or for the difference between
them (for example, the average number of hours teenagers spend watching
TV per week or the percentage of men versus women in the United States
who take arthritis medicine every day). You get the nitty-gritty on how con-
fidence intervals are formed, interpreted, and evaluated for correctness and
credibility. You explore the factors that influence the width of a confidence

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