I am testing mediation in SPSS, and all Baron Kenny steps are satisfied, but I have problem in last step. When I include mediator, F becomes non significant, but beta is significant and effect is smaller after including moderator. Can I interpret this like mediation? Sample size is 126. Dependent variable is disease severity (psoriasis), predictor is Cloninger`s temperament dimension (reward dependence), and mediator is avoidant coping with stress.
I am not an SPSS expert, but from what I am reading from your output you have two models, Model 1 (top) and Model 2 (bottom). Model 2 has an added predictor with a lower F statistic (5.765 --> 2.651). Additionally Model 2 has an R square of 0.067 which is very low. Indicating the model does not have a good impact.
Also, note that for Model 2, your t-statistics are 2.004 (p-val: 0.47) and 1.628 (p-val: 0.106). Both parameters are not significant at the 0.95 confidence level, hence you cannot report
From the reference I've read (http://web.pdx.edu/~newsomj/da2/ho_mediation.pdf)
If X is no longer significant when M is controlled, the finding supports full mediation. If X is still significant (i.e., both X and M both significantly predict Y), the finding supports partial mediation.
Your mediation factor (the added predictor) is not significant in Model 2. That said, I would not conclude there is a significant mediation factor. In order for you to conclude mediation, both factors have to be significant. Hence, you have two choices.
Rule out the effect of mediation
Lower your confidence level to 0.90, and then you can conclude mediation.
I'd be very cautious with option 2, as your are now modeling your analysis around trying to obtain significant results, vs trying to be as truthful to the data (and null hypothesis) as possible.
If I've misinterpreted something in the output, let me know and I'll adjust my answer.