# Tag Info

Accepted

### Difference between Repeated measures ANOVA, ANCOVA and Linear mixed effects model

First there is the question of whether it is OK to use percent change as the outcome. In a regression model with baseline as a regressor this is a very bad idea because the outcome is mathematically ...
• 63.9k

### Difference between two-way ANOVA, factorial ANOVA and ANCOVA: as analogies of linear regression

Compared to one way ANOVA: Two way ANOVA adds one more categorical independent variable to the regression (and possibly the interaction between the two IVs). Factorial ANOVA adds any number of ...
• 125k
Accepted

### GPower: Difference in Sample Size for ANCOVA vs. Repeated Measures ANOVA in clinical trials

This is a topic for seriously misunderstanding G*Power! Thank you for bringing this up. We thought the following was an explanation for the matter: "When calculating the sample size for "...
Accepted

### Justifying a smaller control group in survey study

I think you've answered your own question. If your goal is to independently assess the psychometric properties within the control group, collect enough data to do that. If your goal is only to compare ...
• 9,372
Accepted

### Comparison of 2 groups with covariate

I agree with @Sointu's comment. There is nothing "outdated" about ANCOVA. In what I see it's most often just approached through regression. The techniques aren't alternatives, at least not ...
• 58.5k

### Comparison of 2 groups with covariate

First, as others have pointed out, ANOVA, ANCOVA and linear regression are equivalent. Mathematically, if there are $n$ observations and $p$ independent variables (or predictors, or whatever term you ...
• 125k

### Comparison of 2 groups with covariate

The other answers seem to already address the core question of which techniques to use. As others have mentioned, this seems to be a question that can be easily solved with regression or ANCOVA, and ...
• 15.8k

### Should covariates that are not statistically significant be 'kept in' when creating a model?

We really need more information about your goals to answer this question. Regressions are used for two main purposes: Prediction Inference Prediction is when your goal is to be able to guess at ...
• 160
Accepted

• 1,798

### Two-Way ANCOVA: It is necessary to include a non-significant interaction term in the model?

There is nothing in statistical theory or practice which requires you to include any interaction, or any main effect for that matter. You include in your model the variables which your scientific ...
• 18k

### Why is ANCOVA not appropriate for modelling post-intervention outcome, controlling for baseline

DiD vs. ANCOVA has been discussed in my workplace, a health insurance company, where DiD has been the industry standard for some time. I agree that DiD does not adequately account for regression to ...
• 6,144

### Questions concerning visualizing model results with the R-package visreg

I'm not a huge fan of such plots for presentation. You have one continuous covariate and one continuous response variable, so it's easy to make a scatterplot. Use different symbols and colors to ...

### Using PCA to combine variables in a randomized trial with a baseline and a follow-up measurement

The method of collapsing SBP and DBP into one measure should be guided by subject matter expertise. If you are interested in MAP then compute MAP. PCA is guided by variance maximization not by ...
• 95.7k
Accepted

### Different ways to include pre-test performance as a covariate in a linear mixed-effect regression. Which is correct?

A wide variety of interaction terms could be "correct" here, as comments from Robert Long and COOLSerdash suggest. To decide which if any interaction to use involving the ...
• 95.2k

### ANCOVA vs linear mixed model in R, using different functions gives me different results

To summarise: You've discovered that different packages & functions may implement different methods, so you shouldn't expect to get the same results when you throw your data at a sundry collection ...
• 10.5k