SD_M_n_pooled_from_groups {metaHelper}

Combined Standard Deviation for Multiple Groups

Description

Computes the pooled standard deviation for multiple groups.

Usage

SD_M_n_pooled_from_groups(M, SD, n)

Arguments

M

vector of group means

SD

vector of group SDs

n

vector of group sample sizes

Details

This function also returns the combined mean and the total sample size across all groups. Requires also the mean for all individual groups. If there are only two groups and the mean is not available SDp_from_SD() can be used instead.

Value

Within standard deviation

References

Cochrane Handbook

Rücker G, Cates CJ, Schwarzer G. Methods for including information from multi-arm trials in pairwise meta-analysis. Res Synth Methods. 2017 Dec;8(4):392-403. doi: 10.1002/jrsm.1259. Epub 2017 Aug 25. PMID: 28759708.

Examples

# Compute the Standard deviation for the following grouped data
M <- c(1, 1.5, 2) # Means
SD <- c(2, 3, 2.5) # SDs
n <- c(72, 80, 55) # sample sizes
SD_M_n_pooled_from_groups(M, SD, n)