Analysis of Variance Flashcards

1
Q

Sample Distribution Outlines

A

Normal distribution. Mean of sample distribution is same as pop mean. Sample error of distribution is equal to standard deviation of pop

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2
Q

When are t-tests used

A

When measuring sample means from 2 independent groups

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3
Q

Average t-test Outline

A

Both groups come from normally distributed populations and both populations have equal variance

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4
Q

Welch’s t-test

A

Both groups come from normally distributed populations with unequal variance

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5
Q

Variance Definition

A

Squared average distance from the mean

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6
Q

How do you determine if there’s significant variance between groups

A

Levene’s Test (Equal to F-value) or do t-tests for mean comparisons from independent samples (by observation)

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7
Q

Type 1 Error

A

Alpha inflation. Risk of dismissing valid null-hypothesis. Too many false positives

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8
Q

Relationship between alpha inflation and groups number

A

Group numbers increase, increasing alpha inflation

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9
Q

Analysis Variance Test Outline

A

Way to combat alpha inflation. Tests the equality of all group means in 1 go

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10
Q

Within Group variability Outline

A

Differences between 2 means in a group

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11
Q

Between Group Variability Outline

A

Difference between mean of sample and grand mean

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12
Q

Grand Mean Def.

A

Average of means across independent groups being compared

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13
Q

What is the F value expected to be in the case of variance equality

A

~1

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14
Q

How F Value is Evaluated

A

(Between Group Diff.)/(within group diff.) = (effects of group +error)/(error)

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15
Q

F-distribution

A

Non-symmetrical (must be positive). Shape depends on degrees of freedom of denom/numerator (squared measurements eg variance). Groups of distributions need to be compared. MStotal/MmsWithin group

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16
Q

Sum of Squares (SS) Total

A

Total variation between sum of all squared differences between individual values (within group) and grand mean (between groups)

17
Q

SS Between

A

Variation between groups. Squared diff, between group means and grand mean

18
Q

SS within

A

Variation within groups. Squared diff. between each individual value (result) in group and the mean value of the group

19
Q

Post-hoc comparison

A

Used to find exactly where mean diff lies if F value is significant

20
Q

Method of post-hoc comparison

A

Bonferroni Correction. Divides alpha by no. of pair wise comparisons (note if there are 4 means there are 6 times you have to subtract mean values from eachother (pair wise comparison))

21
Q
A