# [R-meta] Best choice of effect size

Luke Martinez m@rt|nez|ukerm @end|ng |rom gm@||@com
Thu Sep 30 00:32:01 CEST 2021

```Dear All,

To further clarify, the proportion types (my previous email) are used
to score each study participant's performance on the text. Then, each
study reports the "mean" and "sd" of a proportion type for control and
experimental groups (to then compare them with t-tests and ANOVAs).

For example, a study using proportion_type1 (see my previous email)
can provide the following for effect size calculation:

Mean    SD     n
group1   0.45      0.17  20
group2   0.17      0.11  19

The same is true for studies that use raw frequencies to score each
study participant's performance on the text. In such studies, often,
"mean" and "sd" of the  # of corrected items (numerator of the
proportions in my previous email) for control and experimental groups
(to then compare them with t-tests and ANOVAs).

For example, a study using (raw) # of corrected items can provide the
following for effect size calculation:

Mean    SD   n
group1   4.5      1.12  17
group2   4.7      1.59  18

My question is that can I calculate SMD across all such studies given
their intent is to measure the same thing?

Thank you,
Luke

On Wed, Sep 29, 2021 at 12:12 PM Luke Martinez <martinezlukerm using gmail.com> wrote:
>
> Dear All,
>
> I'm doing a meta-analysis where the papers report only "mean" and "sd"
> of some form of proportion and/or "mean" and "sd" of corresponding raw
> frequencies. (For context, the papers ask students to read, find, and
> correct the wrong words in a text.)
>
> By some form of proportion, I mean, some papers report actual proportions:
>
> proportion_type1 = # of corrected items / all items needing correction
>
> Some paper report a modified version of proportions:
>
> proportion_type2 = # of corrected items / (all items needing
> correction + all wrongly corrected items)
>
> There are other versions of proportions and corresponding raw
> frequencies as well. But my question is given that all these studies
> only report "mean" and "sd", can I simply use a SMD effect size?
>
> Many thanks,
> Luke

```