Statistical Analysis with R For Dummies
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The normal distribution family is one of many distribution families baked into R. Dealing with these families is intuitive. Follow these guidelines:
  • Begin with the distribution family’s name in R (norm for the normal family, for example).
  • To the beginning of the family name, add d to work with the probability density function. For the probability density function for the normal family, then, it’s dnorm().
  • For the cumulative density function (cdf ), add p (pnorm(), for example).
  • For quantiles, add q (qnorm(), which in mathematical terms is the inverse of the cdf ).
  • To generate random numbers from a distribution, add r. So rnorm() generates random numbers from a member of the normal distribution family.

The complex relationship between x and f(x) is


If you supply values for μ (the mean), Σ (the standard deviation), and x (a score), the equation gives you back a value for f(x), the height of the normal distribution at x. π and e are important constants in mathematics: π is approximately 3.1416 (the ratio of a circle's circumference to its diameter); e is approximately 2.71828. It's related to something called natural logarithms and to numerous other mathematical concepts.

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About the book author:

Joseph Schmuller, PhD, has taught undergraduate and graduate statistics, and has 25 years of IT experience. The author of four editions of Statistical Analysis with Excel For Dummies and three editions of Teach Yourself UML in 24 Hours (SAMS), he has created online coursework for and is a former Editor in Chief of PC AI magazine. He is a Research Scholar at the University of North Florida.

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