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Stats Second Semester > EFA Theory > Flashcards

EFA Theory Flashcards

1
Q

What is EFA

A

a mathematical technique by which patterns of correlations can be explained by a smaller number of variables (components/factors)

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2
Q

What is usually assumed in an EFA

A

that these components (factors) are uncorrelated.

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3
Q

What does EFA make possible

A

modelling the extent to which measured variables and their co-variability can by explained by a smaller number of latent variables

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4
Q

What does EFA often reach the same solution as

A

PFC

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5
Q

What is EFA confirmatory to

A

The researchers specify a model that is then tested

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6
Q

What are different models compared in

A

Goodness of fit

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7
Q

What is a latent factor or variable

A

Not directly observed, cannot be directly measured
E.g. cognitive ability
and EFA measures different aspects of it

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8
Q

What is the main question of EFA

A

Are those aspects riven by the same underlying principles

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9
Q

What does EFA aim to do

A

Understand the structure of set of variables

Try to find a simple structure

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10
Q

How does an EFA try a simple structure

A

identify relatively independent clusters of variables – reduce large set of variables to smaller subset while keeping information

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11
Q

What are the pre-analysis checks of EFA

A

Correlation matrix

Sample size, number of items

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12
Q

What does EFA extraction measure

A

How many factors

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13
Q

What does ration decide

A

how to best view the soltion

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14
Q

What does naming do

A

Name the factors, how good was the EFA

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15
Q

What does the correlation matrix show

A

Variables that cluster together that are corelated together usually 2 up and down and right to the bottom

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16
Q

Why are some sample size pre-condtions needed

A

because correlations coefficient are less reliable for small samples

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17
Q

How many participants are needed per item

A

N (participants) / P (items): 5:1, 10:1

absolute minimum 100

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18
Q

How many subjects to facts

A

N (subjects) / M (factors): 6:1

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19
Q

How many items to facotrs

A

P (items) / M (factors) : 4:1

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20
Q

What are the two stats checks

A

Sampling adequacy and R matrix

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21
Q

What does the sampling adequancy do

A

measure the extent to which the data is suitable for EFA (is there some common variability that can explained by some factors)

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22
Q

What do the factors =

A

linear combinations of variables

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23
Q

What are the three commonly used ways to extract factors

A

K1 rule
Scree test
Parallel Analysis

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24
Q

What are all the three extract factors based on

A

Eigenvalues

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25
Q

What are eigenvalues

A

Are a measure of the variance explained by a factor (principal component

26
Q

What is assumed about eigenvalues

A

that the more the variance that is explained the better….

27
Q

What do you select with the K1 rules

A

Select all factors with eigenvalue totals >1

28
Q

What is does the scree test plot

A

Plot the eigenvalues against the component number

29
Q

What did Cattell argue the cut off point should be

A

argued that the cut off point should be before the point of inflexion

30
Q

When can scree test visual test be a problem

A

if the plot doesn’t have a clear ‘point of inflexion

31
Q

Which do you count in the scree test

A

Those to the left of the point of infection ignoring the point itself

32
Q

What does parallel analysis do

A

Generate a set of ‘random’ eigenvalues given N (number of participants) and P (number of items)

33
Q

What does parallel analysis extract

A

Extract as many factors as there are observed eigenvalues greater than the random eigenvalues

34
Q

What are the two types of rotation

A

Orthogonal and Oblique

35
Q

What do the types of rotation try and achieve

A

simple structure’ (the maximization of loadings on one factor while minimizing on the other factors).

36
Q

What does orthogonal rotation assume

A

that the factors are not correlated with each other

37
Q

What is the orthogonal rotation

A

Varimax rotation is one kind of orthogonal rotation

38
Q

What does oblique ration assume

A

Assume that the factors are correlated with each other

39
Q

What is a kind of oblique ration

A

Direct Oblimin rotation is one kind of oblique rotatio

40
Q

What type of rotation is more difficult to justify

A

Oblique

41
Q

Why are oblique rotations more difficult to justify

A

since in EFA it is assumed that the correlations between factors are all the same size (just not zero).

42
Q

Where are the factors loadings found

A

In the component matrix

43
Q

What do factor loadings do

A

Place factors into significance

44
Q

What factor loadings are not shown

A

< 3

45
Q

When the numbers are in both 1 and 2 of the component matrix what does that suggest

A

potential cross loading

46
Q

What figures should be considered cross loadings

A

Any loading ≥.3 should be considered a potential cross-loading

47
Q

What figures are not considered as cross loadings

A

If the difference between loading is ≥.2 the variable is regarded as not cross-loading.

48
Q

Define reliability

A

A reliable measure consistently reflects the measured construct.

49
Q

What are the tests of internal reliability

A

Split half test.
Cronbach’s alpha (∈[-∞, 1], α≥.7)
KR-20 (∈[0, 1], KR20≥.9

50
Q

What are the tests of external reliability

A

test-retest: r > 0.7

51
Q

What should be considered when naming factors

A

Theoretical considerations
Size of factor loading
Common sense
Raters

52
Q

Who suggested the recapture item technique

A

Meehl 1971

53
Q

What are the three components of variability

A

Unique - Specific to that variable
Common - Shared with other variables
Error – Random variability

54
Q

What is communality

A

Proportion of variance explained by extracted factors

A measure of ‘common’ variance.

55
Q

What are all communality

A

> .6: N≥100

56
Q

What are communalties

A

5 & only a few factors: N∈[100, 200]

57
Q

What is the commonalties for many factors

A

<500

58
Q

How do you test an EFA

A

Researchers typically now move on to ‘Confirmatory Factor Analysis’ where theoretically specified models are tested directly.

59
Q

How many solutions to a ration is there

A

Infinte

60
Q

What mentality can be added to factors

A

Garbage In Garbage Out

Stats Second Semester (9 decks)

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