calculateSmallSampleSizeAdjustment
Function calculates the Hedges small sample size adjustment for standardized mean effect sizes. It calculates the exact value unless the caller sets the parameter exact to FALSE, or the degrees of freedom is too large.
Function calculates the small sample size adjustment for standardized mean effect sizes
calculateSmallSampleSizeAdjustment(df, exact = TRUE) calculateSmallSampleSizeAdjustment(df, exact = TRUE)
df: A vector of degrees of freedomexact: Default value=TRUE, if exact==TRUE the function returns the exact value of the adjustment(s) which is suitable for small values of df, if exact==FALSE the function returns the approximate version of the adjustment(s). See Hedges and Olkin 'Statistical methods for Meta-Analysis' Academic Press 1985.small sample size adjustment value
small sample size adjustment value
df <- 2 c <- calculateSmallSampleSizeAdjustment(df) df <- c(5, 10, 17) adjexact <- calculateSmallSampleSizeAdjustment(df) # adjexact=0.8407487 0.9227456 0.9551115 # Hedges and Olkin values 0.8408, 0.9228,0.9551 adjapprox <- calculateSmallSampleSizeAdjustment(df, FALSE) # adjapprox=0.8421053 0.9230769 0.9552239 df <- 2 a <- calculateSmallSampleSizeAdjustment(df) # > a # [1] 0.5641896 df <- c(5, 10, 17) adjexact <- calculateSmallSampleSizeAdjustment(df) # > adjexact # [1] 0.8407487 0.9227456 0.9551115 # Hedges and Olkin values 0.8408, 0.9228,0.9551 adjapprox <- calculateSmallSampleSizeAdjustment(df, FALSE) # > adjapprox # [1] 0.8421053 0.9230769 0.9552239 # Another example: df <- c(10, 25, 50) calculateSmallSampleSizeAdjustment(df, exact = TRUE) # [1] 0.9227456 0.9696456 0.9849119 calculateSmallSampleSizeAdjustment(df, exact = FALSE) # [1] 0.9230769 0.9696970 0.9849246
Barbara Kitchenham and Lech Madeyski