Reliability And Validity

Question 1

Reliability

Answer 1

Consistent measurement

Question 2

Validity

Answer 2

Does it measure what it should

Question 3

Internal reliability

Answer 3

Consistency of the measured items
- perfect internal reliability: any set of items from scale could be selected and will provide a measure that is more or less the same as any other group of items
- internal consistency: respondents answer related items similarly
- in some cases measurement that covers several different aspects is desirable (creates low internal consistency)

Question 4

Types of internal realiability

Answer 4

• traditional approach: Pearson correlation (each half is similar)
• split-half reliability: each participants summed scores are calculated separately for both halves of items
• odd- even realiability: one half of items is odd numbered the other even
• spearman-brown formula: estimation of true split half with correlation to length of scale

Reply on particular items in two halves

Question 5

Cronbach Alpha

Answer 5

Average of every possible half correlated to every other possible half
A>0.70 (adequate)
A>0.95 (too high)

Question 6

Realiability coefficients

Answer 6

• removing items causing internal reliability to be lower
• common method: computer cronbach a for total scale and see how it changes when removing items
• stop if satisfactory value is achieved

Question 7

Item total correlations

Answer 7

• correlations of participants score on each item with their overall score
• if all of the individual items on the scale are measuring the same structure, all items correlate with total score on scale
• removing items with low item total correlations
• low item correlation: inconsistent item with possibility measures a diff psych construct

Question 8

Item discrimination between extreme groups

Answer 8

• removing those items which have low discrimination with people scoring low or high
• high reliability: if items are differently answered by highscorers -> item retained
• low reliability: items which highscorers are the same as lowscorers -> item dropped

Question 9

Reliability over time

Answer 9

• consistency of measure at different time across different circumstances
• test-retest reliability:
• > repeated measurement/ longitudinal design
• > longer interval between: more opportunity for within subject
• > carry over effect: test and immediate retest

Question 10

Face validity

Answer 10

You read it and you check if the item measures what you want to measure
High face validity: makes people more motivated but also more prone to lying

Question 11

Content validity

Answer 11

Optimal content validity: careful collections of items that is diverse for the concept being assessed
-> alternative: content validity achieved by experts decision

Question 12

Criterion validity

Answer 12

• exploring wether scores on a given psychological test are successfully related to know criteria
  -> concurrent
  -> predictive

Question 13

Concurrent validity

Answer 13

Assessed against a criterion measuring same construct
- calculating correlation of the test with another test for same construct
- > ideally a strong correlation (but if it’s a new theoretical construct, a lower correlation is better)

Question 14

Predictive validity

Answer 14

• ability of measure to predict future events

Not all measurements intend on predicting future

Question 15

Construct validity

Answer 15

Aim: specify the nature of psychological construct that underlies given measurement
Support for construct validity: depends on assumptions regarding nature of construct

Question 16

Triangulation

Answer 16

Two different measures with same construct will correlate with variable the construct might relate to

-> combination of concurrent and predictive validity
(If A and B correlate-> concurrent)
(If A and B correlate to X -> predictive)

Question 17

Known groups validity

Answer 17

• evidence of optimal validity: can be established that scores on a measure differ in predictable ways between 2 specified groups

Question 18

Convergent validity

Answer 18

-measures of given psych construct should relate irrespective of the nature or more of the measure

Question 19

Discrimination validity

Answer 19

• if measures measure different construct no correlation is expected