Test Scores, Norms, and Score Interpretation

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Test Scores, Norms, and Score Interpretation

Transcript Of Test Scores, Norms, and Score Interpretation

Test Scores, Norms, and Score Interpretation

PSY 721 Scores and Norms

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What We Will Cover in This Section.
• Test scores • Norms
• Types of interpretation

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Raw Score
Count or sum of the number of items endorsed
or number of items correctly answered.

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Norms

Norm Norms Norming

Behavior that is usual or typical for members of a group.
Reference scores against which an individual’s scores are compared.
Process of establishing norms for a test.

Norman

A fat guy who drinks beer in Cheers.

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Establishing Norms

1. Target population. 2. Standardization sample. 3. Norm Group.
- Size. - Geographic representation. - Socioeconomic level. - Ethnic composition.

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2

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Types of Norms

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Reference Groups
• National norms. • Regional norms. • Local norms. • Sub-group norms.

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Table 2. Word, raw score: Total Sample

Valid
Missing Total

5 6 7 8 9 10 11 12 13 14 Total System

Frequency 1 9
24 31 40 12 19 15
1 1 153 11 164

Percent .6
5.5 14.6 18.9 24.4
7.3 11.6
9.1 .6 .6
93.3 6.7
100.0

Valid Percent .7
5.9 15.7 20.3 26.1
7.8 12.4
9.8 .7 .7
100.0

Cumulative Percent .7 6.5 22.2 42.5 68.6 76.5 88.9 98.7 99.3 100.0

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Valid

Table 6. Word, raw score: Undergraduate Students

6 7 8 9 11 12 Total

Frequency 3
14 11
7 1 1 37

Percent 8.1
37.8 29.7 18.9
2.7 2.7 100.0

Valid Percent 8.1
37.8 29.7 18.9
2.7 2.7 100.0

Cumulative Percent 8.1 45.9 75.7 94.6 97.3 100.0

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Valid

Table 9. Word, raw score: Graduate Students

5 6 7 8 9 10 11 12 13 14 Total

Frequency 1 6
10 20 33 12 18 14
1 1 116

Percent .9
5.2 8.6 17.2 28.4 10.3 15.5 12.1
.9 .9 100.0

Valid Percent .9
5.2 8.6 17.2 28.4 10.3 15.5 12.1
.9 .9 100.0

Cumulative Percent .9 6.0 14.7 31.9 60.3 70.7 86.2 98.3 99.1 100.0

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Developmental: Age Norms

• Uses.
– Initially for establishing ‘mental age’.
– BASAL AGE highest age at and below which all tests are passed.

• Issues.
– Mental age units are not constant with chronological age.
– Rapid growth spurts.
– Not an interval scale.
– Cannot be interpreted as overall performance.

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Developmental: Grade Norms

• Uses.
– Educational achievement tests.
– May be expressed in years and months.

• Issues.
– Instructional content varies from school to school.
– Not really relevant at high school level.
– Interpretation.

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Developmental: Ordinal Scales

• Uses.
– Behavioral and cognitive development.
– Piaget. – Gesell.

• Issues.
– Assume one level is prerequisite to the next.

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Major Issue
1. How do you compare performance of different people across different forms of a test?
2. How to compare performance of people on the same test across different administration techniques?

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Equating

Process of establishing the relationship
between scores on alternate forms of a test or the same test across
time.

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Equating: Same Sample Technique

1. Get a large representative sample of examinees.
2. Give half the sample form A and the other half form B.
3. Compute the mean and standard deviation for each form.
4. Compute the z-scores for the raw scores for each test.
5. For ease of interpretation transform the z-scores to some common transformed score.

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Equating: Different Sample Technique

1. Identify a sample of key questions from the earlier test version.
2. Insert these items in the current version of the test.
3. Compare the performance on the key questions across the two groups.

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National Anchor Norms

• Uses
– Compare performance on different tests.

• Issues.
– Does not imply that the tests are interchangeable.
– Different psychometric properties.

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Within Group Comparisons

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Percentile
Percent of people in the standardization sample
who fall at or below a given score.

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Percentiles: Benefits & Issues

• Benefits.
– Easy to compute.
– Easy to understand.
– Suitable to all tests.
– Widely used.
– Good if the distribution is normal.

• Issue.
– Inequality of units at extremes of the normal curve.
– Problem if the distribution is not normal.

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Quartiles
Divides the distribution into four groups each containing
25% of the sample.

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Q1 Q2 Q3

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Standard Scores

A score that has been converted
from one scale into another scale.

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Concept
µ

-2σ -1σ -2z -1z

0σ +1σ +2σ 0z +1z +2z

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z-Scores
z= X− M s

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Example

Mean = 50 SD = 10

What is the z score for a raw score of 65?

What is the z score for a raw score of 45?

Z = (65 –50)/10 Z = 15/10 Z = 1.5

Z = (45 – 50)/10 Z = -5/10 Z = -.5

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ScoreNormsPerformanceTestsPeople