The Power option calculates statistical power and other details about a given hypothesis test.
 • LSV (the Least Significant Value) is the value of some parameter or function of parameters that would produce a certain p-value alpha. Said another way, you want to know how small an effect would be declared significant at some p-value alpha. The LSV provides a measuring stick for significance on the scale of the parameter, rather than on a probability scale. It shows how sensitive the design and data are.
 • LSN (the Least Significant Number) is the total number of observations that would produce a specified p-value alpha given that the data has the same form. The LSN is defined as the number of observations needed to reduce the variance of the estimates enough to achieve a significant result with the given values of alpha, sigma, and delta (the significance level, the standard deviation of the error, and the effect size). If you need more data to achieve significance, the LSN helps tell you how many more. The LSN is the total number of observations that yields approximately 50% power.
 • Power is the probability of getting significance (p-value < alpha) when a real difference exists between groups. It is a function of the sample size, the effect size, the standard deviation of the error, and the significance level. The power tells you how likely your experiment is to detect a difference (effect size), at a given alpha level.
Raw effect size. For details about effect size computations, see the Fitting Linear Models book. The first position is initially set to the square root of the sums of squares for the hypothesis divided by n; that is, .
Solves for the value of the parameter or linear test that produces a p-value of α. This is a function of α, σ, n, and the standard error of the estimate. This feature is available only when the X factor has two levels and is usually used for individual parameters.
 • Adjusted power is the power calculated from a more unbiased estimate of the non-centrality parameter.
 • The confidence interval for the adjusted power is based on the confidence interval for the non-centrality estimate.
Adjusted power and confidence limits are computed only for the original Delta, because that is where the random variation is.
Related Information
 • Example of the Power Option
 • Statistical Details for Power