SMD_from_mean {metaHelper}

Standardized Mean Difference (SMD) from Means and Pooled Standard Deviation

Description

Calculates the SMD. It needs to be provided with the pooled standard deviation. If the pooled standard deviation is not available SMD_from_group() provides a direct method to calculate the SMD and also offers different forms like Hedges' g or Cohen's d.

Usage

SMD_from_mean(M1, M2, SD_pooled)

Arguments

M1

treatment effect size group 1

M2

treatment effect size group 2

SD_pooled

the pooled standard deviation or the standard deviation of the control group in case Glass's delta should be calculated

Details

CAVE: If you want to get Hedges' g it is insufficient to simply pool the standard deviation with SDp_from_SD(). The resulting SMD needs to be further multiplied with the hedges factor. This is done automatically when you use SMD_from_group().

Value

Standardized Mean Differences

References

https://handbook-5-1.cochrane.org/chapter_9/9_2_3_2_the_standardized_mean_difference.htm

Examples

# Mean control = 153, Mean intervention = 136, pooled SD = 25
SMD_from_mean(153, 136, 25)