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Nov 21, 2018 at 6:20 comment added Parthiban Rajendran Also if you make $\mathbf X$ as fixed and known, then in PRF, $E(Y|x)$ becomes simply $E(Y)$?
Nov 21, 2018 at 5:59 comment added Parthiban Rajendran So for regression of $\mathbf Y$ with $X$, $\mathbf X$ is not a Random Variable? (This would also indirectly assert why slope estimator turns out to be normal because its linear combination of $\mathbf Y$, so want to confirm). Screenshot
Mar 26, 2018 at 14:51 comment added gung - Reinstate Monica @AdamO, consider, eg, this situation: Choosing between LM and GLM for a log-transformed response variable, & my answer there.
Mar 26, 2018 at 14:33 comment added AdamO What does this give you? In what sense is it an assumption? For reproducibility, that assumption relaxes the "linearity" (i.e. that the mean model is true) I think we require that the $X$ are obtained from the same probability model. They need not be exactly the same.
Apr 13, 2017 at 12:44 history edited CommunityBot
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Apr 14, 2015 at 14:13 comment added gung - Reinstate Monica @user1205901, the top model is of the data generating process, the bottom is your estimate of it.
Apr 14, 2015 at 8:41 comment added user1205901 - Слава Україні Why do the βs and the ε have a hat in the bottom equation, but not in the top one?
Apr 4, 2013 at 21:18 history edited gung - Reinstate Monica CC BY-SA 3.0
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Dec 9, 2012 at 16:00 comment added gung - Reinstate Monica W/ predictive modeling, that's not quite true, but we will treat our $X$ data that way in the future, when we use the model to make predictions.
Dec 9, 2012 at 16:00 comment added gung - Reinstate Monica @stan, I recognize your confusion. Terminology in stats is often confusing & unhelpful. In this case, "fixed" is not quite the same as the fixed in 'fixed effects & random effects' (although they are related). Here, we're not talking about effects--we're talking about the $X$ data, ie your predictor / explanatory variables. The easiest way to understand the idea of your $X$ data being fixed is to think of a planned experiment. Before you have done anything, when you're designing the experiment, you decide what the levels of your explanatory will be, you don't discover them along the way.
Dec 9, 2012 at 10:22 comment added abc What does it mean "fixed" | "random" in plain language? And how to distinguish between fixed and random effects(=factors)? I think that in my design there is 1 fixed known factor with 5 levels. Right?
Dec 5, 2012 at 14:21 history edited gung - Reinstate Monica CC BY-SA 3.0
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Dec 5, 2012 at 5:27 history answered gung - Reinstate Monica CC BY-SA 3.0