Psychological Testing

Principle Types of Psychological Tests

Mental ability tests Intelligence – general Aptitude – specific

Personality scales Measure motives, interests, values, and attitudes

Key Concepts in Psychological Testing

Standardization Test norms Standardization group

Reliability Correlation coefficient

Validity Content validity Criterion-related validity Construct validity

Classical Test Theory Goal of testing is to identify subject’s “true

score” on a given attribute.

Classical Test Theory says…

Test Score = True Score + Error of Measurement

Goal of test developers is to minimize this!

Sources of Measurement Error

Where do these measurement errors come from?

Item sampling error

Internal consistency error

Time sampling error

Random error

Testing

How do psychologists know how well their test is measuring a person’s true score?

By assessing test reliability

Test-Retest reliability

Internal Consistency reliability

Alternate or Parallel Form reliability

Assesses Time sampling error

Assesses Item sampling errorAssesses

Internal consistency error

Test-Retest Reliability

Q9 Q10 Q17 Q18

Q9 1.0000Q10 .1829 1.0000Q17 .1888 .5718 1.0000Q18 .1730 .4031 .5302 1.0000

Correlation Matrix

Scale Scale Corrected Mean Variance Item- Squared Alpha if Item if Item Total Multiple if Item Deleted Deleted Correlation Correlation Deleted

Q9 8.9250 8.4753 .2220 .0494 .7513Q10 9.4750 6.2272 .5460 .3452 .5655Q17 9.2875 5.3720 .6160 .4367 .5080Q18 9.1750 6.8804 .5141 .2999 .5930

Reliability Coefficients 4 items

Alpha = .6846 Standardized item alpha = .6749

I am carefreeI am rarely overcome with worriesI am not a worrierI rarely feel fearful or anxious

Judging Internal Consistency

Anxiety Scale Items

9. I am carefree10. I am rarely overcome with worries17. I am not a worrier18. I rarely feel fearful or anxious

Testing How do psychologists know their test is

measuring what they think it is measuring?

By assessing test validity Content validity Criterion-related validity Construct validity

Fig. 9-4, p. 339

Fig. 9-5, p. 340

Assessing Construct Validity

Convergent Construct Validity

Correlations

1.000 .477**

.477** 1.000

NEO Extraversion Scale

Class Extraversion Scale

NEOEXTRA CLASSEXTRA

Correlation is significant at the 0.01 level (2-tailed).**.

Our measure of extraversion should be correlated with things related to extraversion

Divergent Construct Validity

Correlations

1.000 .843** -.066

.843** 1.000 .011

-.066 .011 1.000

HEIGHT

SHOE

Class Extraversion Scale

HEIGHT SHOE EXTRA202

Correlation is significant at the 0.01 level (2-tailed).**.

Our measure of extraversion should not be correlated with things unrelated to extraversion

Our measure of impatience should not be correlated with things unrelated to impatience.

Correlations

1.000 .857** -.085

.857** 1.000 .039

-.085 .039 1.000

HEIGHT

SHOE

Impatience Scale

HEIGHT SHOE EXTRA202

Correlation is significant at the 0.01 level (2-tailed).**.

Assessing Construct Validity

Convergent Construct Validity

Our measure of impatience should be correlated with things related to impatience.

Divergent Construct Validity

Correlations

1.000 .275*

.275* 1.000

Impatience Scale ‘02

Impatience Scale ‘03

‘02 ‘03

Correlation is significant at the 0.05 level (2-tailed).*.

Testing Utility of Psychological Tests

Reliability Alternate or Parallel Form Internal Consistency Test-Retest

Validity Content Criterion-Related Construct