I am sorry to ask such basic questions, I am in Southamerica at the moment and my acess to Mplus literature and help in person in limited.
Which modelfit indices are you talking about?
The Output says the folowing: Chi-Square Test of Model Fit (Value = 488.527, df=128, p = .000) Chi-Square Test of Model Fit for the Baseline Model (Value = 1456.747, df=120, p =.000) CFI = 0.730, TLI = 0.747 Loglikelihood: H0 Value = -1790.674, H1 Value = -1546.411 Number of Free Parameters = 22 Akaike (AIC) = 3625.349, Bayesian (BIC)= 3674.178, Adjusted BIC = 3604.899(n* = (n + 2) / 24) RMSEA (Estimate = 0.204, 90 Percent C.I. [0.185,0.223], p(RMSEA <= .05) = .000 SRMR (Value = 0.149)
And which model fit indices indicate, why my model fit is so low, and how do I change that?
Does the model fit only serve to get a higher power for significant results?
Ask for the MODINDICES option of the OUTPUT command. The Mplus User's Guide is available on the website. The Topic 1 course handout and video discuss modification indices. You can also Google modification indices.