A function for estimating the correlation from a paired samples t-test.
Useful for when using tsum_TOST and the correlation is not available.

`extract_r_paired(m1, sd1, m2, sd2 = NULL, n, tstat = NULL, pvalue = NULL)`

## Arguments

- m1
mean of group 1.

- sd1
standard deviation of group 1.

- m2
mean of group 2.

- sd2
standard deviation of group 2.

- n
Sample size (number of pairs)

- tstat
The t-value from a paired samples t-test

- pvalue
The two-tailed p-value from a paired samples t-test

## Value

An estimate of the correlation.

## References

Lajeunesse, M. J. (2011). On the meta‐analysis of response ratios for studies with correlated and multi‐group designs. Ecology, 92(11), 2049-2055