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98 Cards in this Set

  • Front
  • Back

In terms of p value, why is it not as effective as going by effect size?

Because you can just copy and paste the results over and over thereby increasing sample size and the results become significant i.e. not down to chance but only when there are a LOT of participants can the effect be visible. Effect size estimates this without having to use a massive sample.

What is another issue with only using p values?

It is difficult to compare studies that only report p values because of different sample sizes

What is a major flaw of using p values?

They reject logic based on probability ie just because the experimental hypothesis is correct does not mean the null hypothesis is incorrect

What is a major advantage of using effect sizes?

They are standardized, therefore we can make cross study comparisons

What are the three different ways of working out effect sizes?

Partial eta squared, Cohens D, and Pearsons R

How does partial eta appear?

ηp2

What is partial eta squared used in?

ANOVA

What are the small, medium and large values of partial eta squared?

Small = 0.01+
Medium = 0.06+
Large = 0.14+

What is Cohens D used for?

Comparing the magnitude of the means of two tests, often used within t-tests

Which figures are used to calculate Cohens d?

Either the mean and SD of each group OR t value and degrees of freedom HOWEVER this is only for a independent group t-test

What are the small, medium and large levels of Cohens d?

Small = .2+
Medium= .5+
Large = .8+ (note: Cohen’s d can be over 1)


When is Pearsons r used as a measure of effect size?

Comparing the difference between two groups in addition to correlations

How do we interpret pearsons r?

Small =.1+
Medium = .3+
Large = .5+

What does ANOVA stand for?

Analysis of variance

What is ANOVA a form of?

Regression

What is the aim of Anova?

To reduce error rates associated with multiple pairwise comparisons

Within ANOVA, if we need to compare 4 conditions, how many pairwise comparisons would we need to do?

6 pairwise comparisons

Before we do comparisons within ANOVA, what must we do first?

Conduct one test to see if there is a difference overall ie a main effect; if the ANOVA is significant, we then have justification to conduct the comparisons

After we run ANOVA, what do we do?

Look at comparisons between groups using planned comparisons and post hoc tests

What is the one way between subjects ANOVA used for?

Where we need to explore differences between 3 or more independent conditions on a single variable

Give an example of a one way between subjects ANOVA

If we had a theory that hair colour is associated with working memory (one DV), we would compare differences between scores of a working memory test between people with blonde, brown, red and black hair (1 between subjects IV, which has four levels)

What will a one way ANOVA do and what will it not do?

It WILL tell us is there is a significant difference across conditions; it WON'T tell us which conditions significantly differ from each other

What are the three assumptions of between subjects ANOVA?

Homogenity of variance


Normal distribution of data


Interval/ratio data (although ordinal is often also used)

What is the homogenity of varience?

Within each level of the IV, variances should be very similar

What do post hoc tests reveal?

Where exactly significant differences lie

What is Levenes?

A test for homogenity of varience (ANOVA)

Which tests are used to calculate F-values if homogenity of variance is violated within an ANOVA?

Browns-Forsythe and Welch tests

What is the Tamhane’s T2 test?

A post hoc test used when Levene's reveals no homogenity of variance

What is the aim of a Bonferroni correction?

Corrects the p value for each comparison; ie whatever P value SPSS calculates, it corrects it by 3 to make it harder to be significant

Which type of graph is usually used for a one way ANOVA?

A simple bar graph

What do error bars indicate?

The amount of variance the data has around the mean and/or confidence intervals

If the error bars on two separate graphs do NOT overlap, what is it indicative of?

A statistically significant difference

If the 95 % confidence interval bars on a graph do not overlap, what does this indicate?

That they are different

When do we use a one way within subjects ANOVA?

When we have a single within subjects variable with 3 or more levels

What are the assumptions of the within subjects ANOVA?

Normally distributed data


Ratio, interval or ordinal data


Sphericity

What is Sphericity?

Sphericity = equality of variances in DIFFERENCES between levels

A-B variance = 15.75
A-C variance = 16.42
B-C variance = 16.01



Is sphericity assumed here?

Yes

A-B variance = 150.75
A-C variance = 3.12
B-C variance = 147.01



I sphericity assumed here?

No

Why do we not need a homogenity of variance test for a within subjects ANOVA?

Because there is no between subjects factor

Within a one way ANOVA, we do not ask for post hoc tests; what do we do instead?

We ask for estimated marginal means and compare main effects (it will calculate whether there a difference between levels of the ANOVA)

Within an LSD adjustment, which correction is made?

None

What is a between subjects ANOVA? (aka complex ANOVA)

Where we have more than one IV - sometimes many IVs

If you expect a main effect AND an interaction, what do you need?

Power ie sample size

Why is sample size more important when using between subjects ANOVA?

Because each person only gives one score

What are the assumptions of between subjects ANOVA?

Interval/ratio data but ordinal can be used


Homogenity of variance

Why is there only one test statistic that looks at homogenity of variance with a between subjects ANOVA?

Because it compares cells rather than IVs seperately

Within subjects ANOVA requires...

Sphericity

Between subjects ANOVA requires....

Homogenity of variance

What does the Mauchly’s test test for?

Sphericity

What is a common method of doing planned comparisons on a within subjects ANOVA?

T-tests

When is a mixed ANOVA used?

When we have a mix of within subject IVs and between subjects IVs

In which case would we set up a mixed ANOVA?

Where we think there will be the between subjects variable will have a differential effect on the different levels of the within subjects IV

Give an example of a simple mixed ANOVA

The effect of gender on different measures of IQ


Gender (male, female) between subjects
IQ measure (Verbal IQ, non verbal IQ) within subjects

What is the Box's test for a mixed ANOVA?

It compares variances within the two covariance matrices'

What is the difference between Box's test and the other tests?

We want Box’s test to be non-significant (like other ANOVA assumption tests) however, unlike the others it is only an issue if p<.001!

What kind of graph is best for a mixed design?

Clustered bar graph

What is MANOVA?

Multivariate analysis of variance

When do we use MANOVA?

When we have one IV and many DV's

Give an example of the kind of experiment a MANOVA would be used for

The effect of pet ownership (one IV) on mental health (many DV's ie anxiety, depression, eating disorders, OCD, etc etc)

Why not just run many ANOVA's rather than one MANOVA?

Because more DVs increases the risk of a type 1 error

What does the MANOVA assess?

Whether or not your IV has an OVERALL effect on your variables taken together, after which you can look closer and see WHICH variables it effects

In a multivariate ANOVA will the IV will always be within or between subjects?

Between subjects

What kind of homogenity of variance test will be calculated?

Levene’s will be calculated for each DV (you want them to be non-sig)

MANOVA will produce two homogenity tests; which?

Box's and Levene's

If the Box's test produces a NON sig result, what does this mean?

That the p value taken from the multivariate test box in the output is reliable

If Levene's test produces a NON sig result, what does this mean?

That each p value for each DV taken from the between subjects contrasts box is reliable

In addition to a F value, degrees of freedom and a p value, which other four measures are given in an ANOVA?

Pillai's Trace


Wilks' Lambda
Hotelling's Trace
Roy's Largest Root

Why would a Tamhane’s T2” test be used within a MANOVA?

Where one variable violates the assumption of equality of variances

What does ANCOVA stand for?

Analysis of Covariance

What are covariates?

Covariates are simply variables that are associated with your DV but are not part of your experimental manipulation

Give an example of a covariate

Effect of alcohol (placebo/low dose/high dose) on working memory or age

What are two common mistakes people make with ANCOVA?

- Throw in as many covariates as possible


- Put in cetergorical variables e.g. gender, racial group

We use a covariate to reduce...

...within group error variance

What does reducing within group error variance mean?

You are more likely to find a significant effect of your manipulation (proportion of between group variance to within group error variance will increase).

What do covariates do to confounds?

Reduces them (more control!)

What is the independence of the covariate and the IV effect?

The covariate should be not be different across the IV groups meaning if you did a ANOVA on the covariate (DV) and group (IV) there would be no significant effect

What is meant by the homogenity of variance slope?

Where the relationship between the covariate and the DV is consistent across groups, e.g


if age was negatively associated with working memory in the placebo it would have to be negatively associated with working memory in the low and high dose conditions

We conduct a within subjects ANOVA and the variances in the differences between scores in each condition are similar. This means....

We have sphericity

The bigger an F statistic the...

...smaller the df

The multivariate test statistic in MANOVA tells us

The overall effect of the IV

A 3x3 ANOVA would produce how many post hoc comparisons for the interaction?

9

We run an ANCOVA when...

When we think a variable will affect our DV

Rank the following effect sizes from the smallest to the largest: Partial eta squared = .06; d = .2; r = .5

.06, .5, .2

Name an example of an invalid covariate


Religion

You run an experiment with gender, experimental condition (warm room, mild room and cold rom) as between subjects factors and working memory, IQ, and verbal fluency as dependent variables. What would be the appropriate analysis

2x3x3 mixed ANOVA

An effect size of r=.3 is...

Medium/moderate effect

What is wrong with the following F(36,2)=4.68, p=.002, ηp2 = .29

The df is too large

When graphing data what would be appropriate for error bars

95% confidence intervals

Box’s test is a concern when...

p<.001 as it's highly sensitive

You produce a Bonferroni corrected p value of .3 for a comparison following a univariate ANOVA with an IV with 4 levels, what would be the non corrected p value?

.005

When doing a Bonferroni, SPSS multiplies a calculated p by the number of what?


Comparisons, which we
compare to the standard critical p of .05.

We run a 3 x 4 x 2 ANOVA and use the least significant difference test to explore a three way interaction. What may this cause

Type 2 errors

What is a type 1 error?

Detecting an effect that isn't there

What is a type 2 error?

Failing to detect an effect that is there

Effect sizes are useful if we...

Want to see what manipulation across different studies causes biggest effects

If the p value for Box’s test statistic is .01 you have

Have homogeneity of covariance matricies

Larger F values are likely to be associated with..

Smaller p values. The larger your F value, the easier it is for your results to be significant

A covariate is useful if wish to...

Reduce error variance