www.statsoft.com

Electronic statistics textbook banner

Statistical Advisor, How To Find Shape of (or Fitting) Distributions

Use one of the following:

NONPARAMETRICS & DISTRIBUTIONS: This chapter describes techniques for plotting and comparing the observed distribution of variables against several theoretical distributions such as the normal distribution, the exponential distribution, the gamma distribution, the log-normal distribution, the Chi-square distribution, the binomial distribution, geometric distribution, etc. Statistical significance tests are described for evaluating the discrepancy of the observed data from the respective theoretical distributions (Chi-square test, Kolmogorov-Smirnov test). In addition, this chapter describes how to fit any set of predicted (hypothesized or expected) frequencies to observed frequencies.

SURVIVAL ANALYSIS: This chapter describes techniques for fitting special distributions to censored survival/failure times (Weibull, Gompertz, linear and exponential hazard). A data set is said to be 'censored' if some observations are incomplete, but not missing. For example, in industrial reliability testing, a part or product may not fail (break) within the time span covered by a study. However, we do not know how long it will function properly thereafter, and thus, that observation is 'censored.'

GRAPHICAL ANALYTIC TECHNIQUES: Graphical analytic techniques include various curve fitting routines.