Statistical Analysis with R For Dummies

Chapter 8

What’s Normal?

IN THIS CHAPTER

Meeting the normal distribution family

Working with standard deviations and the normal distribution

Understanding R's normal distribution functions

One of the main jobs of a statistician is to estimate characteristics of a population. The job becomes easier if the statistician can make some assumptions about the populations he or she studies.

Here’s an assumption that works over and over again: A specific attribute, ability, or trait is distributed throughout a population so that (1) most people have an average or near-average amount of the attribute, and (2) progressively fewer people have increasingly extreme amounts of the attribute. In this chapter, I discuss this assumption and its implications for statistics. I also discuss R functions related to this assumption.

Hitting the Curve

Attributes in the physical world, like length or weight, are all about objects you can see and touch. It’s not that easy in the world of social scientists, statisticians, market researchers, and businesspeople. They have to be creative when they measure traits that they can’t put their hands around — like “intelligence,” “musical ability,” or “willingness to ...