Unit 12 ANCOVA

Question 1

What does ANCOVA stand for

Answer 1

Analysis of covariance

Question 2

The F-test is calculated by

Answer 2

Dividing the explained variance between groups by the unexplained variance within the groups
F = MSbetween/MSwithin
If this value is larger than a critical value, we conclude
that there is a significant difference between groups.

Question 3

5 assumptions of ANCOVA

Answer 3

1. Linearity of regression
2. Homogeneity of error variances
3. Independence of error terms
4. Normality of error terms
5. Homogeneity of regression slopes

Question 4

ANCOVA is

Answer 4

A general linear model which blends ANOVA and regression.

Question 5

What does ANCOVA evaluate

Answer 5

ANCOVA evaluates whether population means of a dependent variable are equal across levels of a categorical independent variable often called a treatment, while statistically controlling for the effects of other continuous variables that are not of primary interest aka covariates.

Question 6

The ANCOVA procedure is described as follows:

Answer 6

Assuming that a linear relationship between the response (dependent variable) and covariate exists.
yij = µ + τi + B(xij − xi) + ϵij

Question 7

Covariation is when…

Answer 7

..one continuous variable is correlated to another continuous variable

Question 8

Dependent variable is

Answer 8

Continuous (scale/interval/ratio).
Our response variable, what we measure

Question 9

Independent variables are

Answer 9

Categorical factors or explanatory variables
Covariates: continuous variables that can explain variability in dependent variable or block/control confounding factors

Question 10

Conditions/assumptions of ANCOVA

Answer 10

Dependent & covariate measured on continuous scale
Independent variable w/ at least 2 categorical, independent groups.