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jonas helao posted on Tuesday, November 19, 2019 - 8:55 am
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1) I have a binary X, a continuous M (standardized with its sample mean and standard deviation) and a continuous Y (which is also standardized with its sample mean and standard deviation). No missing values. Is the following a correct interpretation of the indirect effect? “there is a 'z' standard deviation decrease of Y (in terms of a sample standard deviation of Y) when X goes from 0 to 1” 2) a continuous X (standardized with its sample mean and standard deviation), a binary M and a continuous Y (standardized with its sample mean and standard deviation). I give two values of the continuous X (0 and +1 SD). Is the following a correct interpretation of the total natural indirect effect? “there is a “z” sample standard deviation decrease of Y (in terms of Y) when X goes from 0 to 1 sample standard deviation of X” |
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Looks ok. Note that for the two continuous X values, they should be in the order +1SD, 0. |
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Dear Dres M&M, I would like to conduct a mediation analysis on the impact of the Big Five on a dichotomous outcome with three mediators. Each Big Five factor is determined by three observed variables. All Big Five should be independent latent variables simultaneously, because I want to control the effects of the remaining as covariates. Now I get the warning message that too many Integration Points are needed. Monte Carlo takes hours and hours. What else can I do? 1) calculate the average of the observed variables for each of the 5 factors, thus virtually eliminating the latent factors 2) Perform 5 individual analyses for the Big Five, each with one factor (although this would no longer be controlled for the other four factors) Many thanks and best regards Stefan |
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Your screen printing says how many dimensions of integration you have. Perhaps it is 5 which is a lot. This means that you don't want to use the default of 15 points per dimension - instead try integration = montecarlo(5000); With integration, the computation speed is also affected by the number of observations. |
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Thanks for the hint, Bengt, the calculation time is now about 2 hours (which is great). But what I don't understand (and what is not described in the UG or in the Mediation and Regression Book): a) what exactly do "integration points" mean? b) what is the meaning of "X points per dimension"? c) does the estimate become less accurate if Monte Carlo is chosen? d) can I also get Bootstrap CI with "Integration: Monte Carlo"? Many thanks and best regards Stefan |
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a-b) See e.g. the 1981 Psychometrika article by Bock & Aitkin. c) Typically not. d) Yes, but it will be slow. You can instead use Estimator = Bayes for which you get non-symmetric CIs which I assume is the reason you want bootstrapping. |
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Thank you very much. |
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Numerical integration is also described in our User's Guide on pages 526 and on. We also discuss it in one of our Short Course Topic videos. |
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