For one part of my thesis I have formulated two hypotheses (in short):
- Gender does not have any effect on efficiency
- The effect of gender on efficiency does not significantly differ between the profit status' of MFIs
OER = Defined as an MFIs efficiency
PF = percentage of women borrowers
dumPP = 0 if non-profit , 1 if for-profit
Code:
. xtreg OER TA1M PSK MFIage c.PF##dumPP dumRP dum2006PF, robust Random-effects GLS regression Number of obs = 143 Group variable: numMFI Number of groups = 48 R-sq: within = 0.0921 Obs per group: min = 1 between = 0.1891 avg = 3.0 overall = 0.0972 max = 9 Wald chi2(8) = 53.86 corr(u_i, X) = 0 (assumed) Prob > chi2 = 0.0000 (Std. Err. adjusted for 48 clusters in numMFI) ------------------------------------------------------------------------------ | Robust OER | Coef. Std. Err. z P>|z| [95% Conf. Interval] -------------+---------------------------------------------------------------- TA1M | -.0028577 .0013633 -2.10 0.036 -.0055298 -.0001856 PSK | .0293177 .0266599 1.10 0.271 -.0229346 .0815701 MFIage | -.0022455 .0057635 -0.39 0.697 -.0135418 .0090509 PF | .4711311 .1959322 2.40 0.016 .0871111 .8551511 1.dumPP | .278675 .1908222 1.46 0.144 -.0953297 .6526797 | dumPP#c.PF | 1 | -.3597447 .2193317 -1.64 0.101 -.789627 .0701376 | dumRP | .041475 .0602707 0.69 0.491 -.0766535 .1596034 dum2006PF | .0807376 .0392052 2.06 0.039 .0038969 .1575783 _cons | .3151538 .1802078 1.75 0.080 -.0380471 .6683546 -------------+---------------------------------------------------------------- sigma_u | .12275084 sigma_e | .11450364 rho | .53471907 (fraction of variance due to u_i) ------------------------------------------------------------------------------
Code:
. quietly margins, dydx(dumPP) at (PF=(0(0.1)1)) vsquish
Code:
. marginsplot, yline(0)
I've also included the regression without the interaction term:
Code:
. xtreg OER TA1M PSK MFIage PF dumPP dumRP dum2006PF, robust Random-effects GLS regression Number of obs = 143 Group variable: numMFI Number of groups = 48 R-sq: within = 0.0941 Obs per group: min = 1 between = 0.0857 avg = 3.0 overall = 0.1079 max = 9 Wald chi2(7) = 42.03 corr(u_i, X) = 0 (assumed) Prob > chi2 = 0.0000 (Std. Err. adjusted for 48 clusters in numMFI) ------------------------------------------------------------------------------ | Robust OER | Coef. Std. Err. z P>|z| [95% Conf. Interval] -------------+---------------------------------------------------------------- TA1M | -.003148 .0014683 -2.14 0.032 -.0060259 -.0002701 PSK | .0293754 .0255809 1.15 0.251 -.0207624 .0795131 MFIage | -.0016013 .006634 -0.24 0.809 -.0146036 .0114011 PF | .1932328 .0901735 2.14 0.032 .0164959 .3699696 dumPP | -.002885 .0742708 -0.04 0.969 -.148453 .142683 dumRP | .0547621 .0585926 0.93 0.350 -.0600773 .1696015 dum2006PF | .0706054 .0344676 2.05 0.041 .0030501 .1381606 _cons | .5389458 .1261681 4.27 0.000 .2916608 .7862307 -------------+---------------------------------------------------------------- sigma_u | .13503925 sigma_e | .11413315 rho | .58331564 (fraction of variance due to u_i) ------------------------------------------------------------------------------
Am I right to assume the following:
1. As -marginsplot- shows, dumPP does not have, at any point, any proven significant impact on the effect gender has on efficiency
2. Regression 1 implies that although the effect of gender is somewhat weaker in for-profit MFIs than it is in non-profit MFIs, the effect gender has on efficiency is similar. Again I expected coefficients to change with addition of the interaction term, as it redefines the meaning of PF. Given
0.4711311PF - 0.3597447PF*numPP
Effect of PF in non-profit MFI: 0.47
Effect of PF in for-profit MFI: 0.11
Effect of PF in second regression: 0.19
On the one hand, the model does not estimate the interaction term to be significant, -marginsplot- does not imply any significant impact of dumPP on the linear prediction concerning PF, and PF does stay significant in both regressions. On the other hand, coefficients do vary quite a bit between non-profit and for-profit MFIs.
Is this a case where I could argue both ways given my interpretation, or is there some obvious approach I have missed?
My interpretation would be that although the effect of PF is different between non-profit and for-profit MFIs, this difference is not significant. Thus, there is no evidence that would suffice for a rejection of H2.
I have also included some summary statistics for OER for comparison.
Code:
. tabstat OER, stat(mean q min max) variable | mean p25 p50 p75 min max -------------+------------------------------------------------------------ OER | .6897555 .5999919 .6730029 .768463 .2283214 1.283038 --------------------------------------------------------------------------
0 Response to Interpretation of interaction effect with -margins-
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