When I calculate Effect Sizes (Cohen's d) on the same study using different methods I get completely different effect sizes.
For example: (t=4.81, P<0.001, d=0.41)
I also calculated d=0.41 using reported means and standard deviations, i.e.:
But, using just the t value and sample size of 16, I get 1.76:
0.41 and 1.76 are vastly different. Are these both Cohen's d, and if so, aren't they supposed to be equivalent?