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Student's t-test assumes that the sample means being compared for two populations are normally distributed, and that the populations have equal variances.Welch's t-test is designed for unequal population variances, but the assumption of normality is maintained. [1]
Pearson's correlation coefficient is the covariance of the two variables divided by the product of their standard deviations. The form of the definition involves a "product moment", that is, the mean (the first moment about the origin) of the product of the mean-adjusted random variables; hence the modifier product-moment in the name.
where n 1 is the sample size for sample 1, and R 1 is the sum of the ranks in sample 1. Note that it doesn't matter which of the two samples is considered sample 1. An equally valid formula for U is = (+) The smaller value of U 1 and U 2 is the one used when consulting significance tables. The sum of the two values is given by
Suppose that we take a sample of size n from each of k populations with the same normal distribution N(μ, σ 2) and suppose that ¯ is the smallest of these sample means and ¯ is the largest of these sample means, and suppose S 2 is the pooled sample variance from these samples. Then the following random variable has a Studentized range ...
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Gamma correction or gamma is a nonlinear operation used to encode and decode luminance or tristimulus values in video or still image systems. [1] Gamma correction is, ...
In mathematics, a continuity correction is an adjustment made when a discrete object is approximated using a continuous object. Examples. Binomial If a ...
An alternative correction that is believed to be less conservative is the Huynh–Feldt correction (1976). As a general rule of thumb, the Greenhouse–Geisser correction is the preferred correction method when the epsilon estimate is below 0.75. Otherwise, the Huynh–Feldt correction is preferred. [3]