Statistics How To

Reliability and Validity > Alternate Forms Reliability Alternate forms reliability is a measure of reliability between two different forms of the same test. Two equivalent (but different) tests are administered, scores are correlated, and a reliability coefficient is calculated. A…

Statistical Process Control > A c chart is a type of control chart that shows how many defects or nonconformities are in samples of constant size, taken from a process (Misra, 2008). Formulas The c chart formulas are (Doty, 1996):…

Statistics Definitions > What is Kernel Density Estimation? In non parametric statistics, a kernel is a type of weighting function used for estimating probability density functions. You can think of it as a function that spread’s a data point’s influence…

Descriptive Statistics > An area chart is an extension of a line graph, where the area under the line is filled in. The “lines” are actually a series of points, connected by line segments. As well as looking slightly different…

Statistics Definitions > The Bertrand Paradox is a prime example of how two words—”random” and “equal probability” are incorrectly used to mean the same thing. The paradox shows that if you don’t define your probabilities well, then the mechanism that…

Statistics Definitions > Asymptotic normality is a property of an estimator. “Asymptotic” refers to how an estimator behaves as the sample size gets larger (i.e. tends to infinity). “Normality” refers to the normal distribution, so an estimator that is asymptotically…

Probability Distributions > The Dagum distribution (also called the Inverse Burr distribution; Dagum called it the generalized logistic-Burr distribution) was proposed by Camilo Dagum in the 1970s to model income and wealth distribution. Dagum developed the models as an alternative…

Statistics Definitions > A complete statistic T “… is a complete statistic if the family of probability densities {g(t; θ) is complete” (Voinov & Nikulin, 1996, p. 51). The concept is perhaps best understood in terms of the Lehmann-Scheffé theorem…

Statistics Definitions > Prevalence in statistics Prevalence is the number of disease cases in a population; incidence is number of new cases that develop. Contents: What is Incidence in statistics? What is Prevalence in statistics? 1. Incidence Definition Incidence is…

Probability Distributions > The Kumaraswamy distribution is a two-variable family of distributions that is bounded at one and zero. It is flexible and can be used to model a variety of shapes, and its probability density function and cumulative distribution…