[U] User's Guide

16 [ U ] 1 Read this—it will help7. anova and manova now use Stata’s new factor-variable syntax, which means new estimation andpostestimation features and a few changes to what you type.a. In other estimation commands, covariates are assumed to be continuous unless i. is specifiedin front of variable names. In anova and manova, covariates are assumed to be factors unlessc. is specified.b. To form an interaction, you now use varname#varname rather than varname*varname. A *now means variable-name expansion. A | continues to be used to indicate nesting.c. varname1##varname2 can now be specified to indicate full factorial layout, i.e, varname1varname2 varname1#varname2. You can use varname1##varname2##varname3 to form 3-wayfactorial layouts, and so on.d. No longer allowed are negative and noninteger levels for categorical variables. Options category(),class(), and continuous() are no longer allowed; instead, factor-variable notationsi. and c. are used where there might be ambiguity.e. Reporting option regress is no longer allowed. To redisplay results, use the regress commandafter anova, or the mvreg command after manova.f. Option detail is no longer allowed nor necessary. Output produced by anova and manova isself explanatory, and you can use regress or mvreg if you want factor-level information.g. Option noanova is no longer allowed. To suppress output, type quietly in front of thecommand just as you would with any other estimation command.h. New option dropemptycells makes anova and manova more space efficient by droppingfrom e(b) and e(V) any interactions for which there are no observations. The disadvantage isthat new postestimation command margins then cannot identify nonestimability and issue theappropriate warnings; see [R] margins.i. The following postestimation commands now work after anova just as they do after regress:dfbeta, estat imtest, estat szroeter, estat vif, hausman, lrtest, margins, predictnl,nlcom, suest, testnl, and testparm. Full estat hettest syntax is now allowed,too.j. The following postestimation commands now work after manova just as they do after mvreg:margins, nlcom, predictnl, and testnl.k. Existing command test used after anova now allows all the syntaxes allowed after regresswhile continuing to allow the special syntaxes for anova.l. Existing command test used after manova now allows all the syntaxes allowed after mvregwhile continuing to allow the special syntaxes for manova.Old anova and manova syntaxes continue to work under version control. See [R] anova and[MV] manova.8. Concerning the bootstrap and jackknife prefix commands:a. They may now be used with anova and manova.b. bootstrap’s new option jackknifeopts() allows options to be passed to jackknife forcomputing acceleration values for BCa confidence intervals.c. bootstrap no longer overwrites the macro e(version), which the command being prefixedsaved.