CH 6 ANOVA

indicates that the variation within the groups is greater than the variation between group means

A small F (F < 1)

Which of the following is used to measure effect size for an ANOVA?

Eta squared

The test statistic for an ANOVA is called the ____

F ratio.

T/F ANOVA indicates which group mean is different.

False. Only post Hoc Tests do this

True or False: A two-way ANOVA involves calculating a single F statistic to determine if there is a statistically significant difference in the means.

False; a two-way ANOVA calculates 3 different F ratios: one for each main effect and one for the interaction effect.

A _______ effect is the individual effect of each variable in a two-way ANOVA, whereas the ______ effect is the combined effect of independent variables.

Main; interaction

dfwn= N-k what is N? what is K?

N is the total number of scores in the entire study and k is the number of levels. In the statistics exam example, there are five scores in each of the three groups. Thus, N = 15 and k= 3

What is another name for effect size in an ANOVA?

Proportion of variance accounted for

Which of the following statements is TRUE? A two-way ANOVA is almost exclusively performed using statistical software.

The calculations involved in a two-way ANOVA are tedious and time-consuming, so it is preferable to use statistical software to run this type of analysis.

The null hypothesis in a ANOVA states that...

There is no difference between the mean (dependent variable) based on the different levels (independent variable)

A one-way ANOVA is typically used to determine whether.....

a difference exists between three or more means.

An ANOVA looks for differences ____ and also differences _____

between groups, within each group

In an ANOVA, the independent variable is called a ___

factor

When using a one-way ANOVA, what are the assumptions made about the data?

"SIN" Samples have equal variances Independent samples (independent from each other) Normally distributed population

_____ uses sample statistics to draw conclusions or make inferences about populations

ANOVA analysis of variance

Why are post hoc tests run in conjunction with an ANOVA?

Answer: The results of an ANOVA only provide evidence of whether or not at least one mean is different in a sample of three or more means. The results do not indicate where the difference actually exists. Therefore, post hoc tests are used to determine where specific differences exist.

Why is performing an ANOVA with post hoc tests preferred over running multiple t-tests?

Answer: Using several t-tests to examine differences between three or more means would increase the experiment-wise error rate far above the α level. Therefore, a one-way ANOVA is an appropriate test to run when comparing three or more means because it uses a single value to determine significance.

The alternative hypothesis in a ANOVA states that...

At least one of the means is different from the others

What is the term used to describe complex experimental designs that investigate the effects of more than one independent variable?

Factorial designs

T/F A t-test and ANOVA have a different structure. T/F An ANOVA uses the variance of each sample (squared distance from the mean) in order to compare samples to each other.

False. Similar True.

The likelihood of a Type I error being made at some point throughout an experiment is known as

experiment-wise error rate

Since using multiple t-tests increases the ______, an ANOVA is an appropriate test to run when comparing three or more means.

experiment-wise error rate (type 1 error, 14.26% if running 3 t-tests)

A _______ refers to an independent variable in an ANOVA, whereas a _____ refers to each treatment condition.

factor, level

Studies that have at least two independent variables are referred to as _____

factorial designs

The type of ANOVA used to analyze a dataset depends upon the number of _____ measured in a study

factors (independent variables)

The ____ the value of F-ratio, the more likely it is that a true difference exists between the group means

greater

The combined effect of all independent variables (or treatments) on the dependent variable (or outcome) is

interaction effect

Each factor has a number of ____, represented by the variable ____.

levels, k

The _____ considers how a single independent variable (plant type or fertilizer brand) affects the dependent variable (plant growth)

main effect

To determine each variable's main effect, the _____ of each main effect (average of the means) is compared.

marginal average

used when testing the effect of one independent variable, or factor

one-way or one-factor ANOVA

The simplest ANOVA uses a ____

single-factor, independent measures designt

Unlike a two-sample ______, which is limited to two groups, an ___ can be used to compare two or more groups

t-test, ANOVA

The F ratio compares

the variance between each group to the variance within each group (variance between samples/ variance within samples)

the effects of two factors (independent variables) are assessed by comparing group means

two-way ANOVA

the squared distance from the mean is known as the

variance

T/F Quasi-independent variables, such as age, gender, religion, etc. can also be factors in an ANOVA.

True

T/F The goal of a two-way ANOVA is to determine both the effect of each factor individually and also whether or not there is evidence of a combined effect of the factors acting simultaneously on the dependent variable.

True

T/F Though an ANOVA can be used to compare two groups, it is much more common to use a t-test to do so.

True

T/F The chances of a Type I error remain at 5% since the ANOVA compares the differences using a single statistic.

True.

In a ____ ANOVA, the means of each condition are compared across all conditions

Two-Way

indicates that the variation between the group means is greater than the variation within the groups

a large F (F > 1)