Introduction - a summary of chapter 1 of A conceptual introduction to psychometrics by G, J., Mellenbergh

A conceptual introduction to psychometrics
Chapter 1
Introduction

Test definitions

Psychometric terminology sometimes differs depending on the types of test applications.

A psychological or educational test: an instrument for the measurement of a person’s maximum or typical performance under standardized conditions, where the performance is assumed to reflect one or more latent attributes.

• A test is defined to be a measurement instrument. It is for measurement in the first place.
• A test is defined to measure performance. Two types of performance:
  • Maximum performance tests ask the person to do his or her best to solve one or more problems. The answers to this problems can vary in correctness.
  • Typical performance tests asks the person to respond to one or more tasks where the responses are typical for the person. The person’s responses cannot be evaluated on correctness, but they typify the person.
• Performance is measured under standardized conditions.
• Test performance must reflect one or more latent attributes. The test performance is observable, but the latent attributes cannot be observed.

Tests are distinguished form surveys. It is not assumed that survey questions reflect a latent attribute.

Subtest: an independent part of a test.
A (sub)test consists of one or more items.
Item: the smallest possible subtest of a test. The building blocks of a test.
A test consists of n items, and is called a n-item test.

One or more latent attributes effect test performance.
The number of latent attributes is the dimensionality of the test.
Dimensionality: equal to the number of latent attributes (variables), which effects test performance.

Unidimensional test: a test that predominantly measures one latent attribute.
Multidimensional test: a test that measures more than one latent attribute.
Two-dimensional test: a test that measures two latent attributes. And so on…

Test types

Psychological and educational measurement instruments are divided into:

• Mental test: consists of cognitive tasks
• Physical test: consists of instruments to make somatic or physiological measurements

Maximum perfromance tests

A performance can be considered maximum in two different respects. If the performance is accurate and if the performance is fast.

Classified according to time:

• Pure power test: consists of problems that the maker tries to solve. The test maker has ample time to work on each of the test items, even on the most difficult ones.
  Emphasis on measuring the accuracy to solve the problem.
• Time-limited power tests: test are constructed so that the majority of test takers have enough time to solve the problems, and only a small minority needs more time.
• Speed test: measures the speed taken to solve problems. Usually, the test consists of very easy items that can be solved by all the test makers.
  The test taker is asked to solve the problems as quickly as possible.
  The emphasis is on measuring the time taken to solve problems.

Maximum performance tests are also classified according tot the attributes which they measure.

• Ability test: an instrument for measuring a person’s best performance in an area that is not explicitly taught in training and educational programs.
• Achievement tests: an instrument for measuring performance that is explicitly taught in training and educational programs.

Typical performance tests

A typical performance test: an instrument for measuring behavior that is typical for the person.
Frequently, typical performance tests are called questionnaires or inventories.

Three main types

• Personality tests (questionnaires): measure a person’s personality characteristics
• Interest inventories: measure a person’s interests
• Attitude questionnaires: measure a person’s attitude towards something.

Types of test taking situations

• The test taker is the same person as the one who is measured
• The test taker is a person other than the one being measured