statai

statai - ttest y by(xcat1 ttest y by(xcat1 unequal if one...

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Introduction to Regression Analysis with Stata [stata_intro_regr] 1. Do graphical & numerical univariate summaries 2. Do bivariate graphical & numerical summaries, as follows: mark complete markout y x1 x2 x3 xcat1 xcat2 tab complete Categorical vars tab xcat1 xcat2 if complete==1, cell|col|row chi2 [or: tab xcat1 xcat2, cell|col|row chi2 miss ] Quantitative vars gr y x1 x2 x3 if complete==1, box gr y x1 x2 x3 if complete==1, con(m) band(5) xlabel ylabel pwcorr y x1 x2 x3 if complete==1, obs bonf sig star(.05) or without significance tests & bonferroni adjustment: cor y x1 x2 x3 [which automatically excludes missing values] sort xcat1 by xcat1: gr7 y, hist norm by xcat1: gr7 y, box total tab xcat1: su(y) or: bys xcat1: su y table xcat1, contents(mean y med y sd y min y max y)
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Unformatted text preview: ttest y, by(xcat1) ttest y, by(xcat1) unequal if one sd is 2+times>other sd oneway y xcat1, table bonf mutilevel categorical var; if sd’s test sig as highly unequal, categorize y by one of the following procedures & compute cross-tab sort y xtile xy=y, nq(4) bys xy: su y tab xy xcat1, cell|col|row chi2 sort y gy=group(4) bys gy: su y tab gy xcat1, cell|col|row chi2 3. Estimate the regression model & display four diagnostic graphics reg y x1 x2 x3 rvfplot, yline(0) xla yla predict yhat qnorm yhat, grid avplots sort id lvr2plot, s([id]) 4. Re-estimate the regression model excluding the outlying observations & display four diagnostic plots reg y x1 x2 x3 if id~=91 & id~=126 rvfplot, yline(0) xla yla predict yhat qnorm yhat, grid avplots sort id lvr2plot, s([id])...
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statai - ttest y by(xcat1 ttest y by(xcat1 unequal if one...

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