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Summary Psychometrics, ISBN: 9781506389875 Test Theory
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Test TheoryChapter 1:
Psychometrics and the Importance of Psychological Measurement
Everyone has been affected by psychological measurement in some way in industrialized
societies. It can have a big impact on people and on lives.
These measurements can be used to detect intellectual disability:
general intellectual functioning that is significantly subaverage.
Psychological tests can figure out whether someone has this; when someone scores below a
70 on a IQ test. Someone who scores below 70, cannot get the death penalty in some
countries and states. Because of this, they should be of great quality.
Psychometrics are the principles and concepts important for creating these tests.
People using these tests and their outcomes for work or in some important field in life need
to be able to interpret the results. You need to understand the tests, the outcomes and the
way they are conducted, which has to happen well.
The properties making a good tests have to be clear, just like the attributes of the
instruments.
Observable behavior and unobservable psychological attributes
Tests are used to measure observable events, like behaviors. However, unobservable
behavior is even more interesting, like intelligence or special traits. However, for this they
also usually use behavior. 3 things used to measure working memory:
1. Making an inference from an observable behavior to an unobservable psychological
attribute. We think this reflects working memory. It has to be valid.
2. For it to be valid, the task must be theoretically linked to working memory. Therefore,
measurement usually involves some sort of theory
3. We assume that working memory is more than a figment of our imagination.
Working memory is a theoretical concept that we think explains differences in behavior.
These concepts are referred to as hypothetical constructs/ latent variables.
Theoretical psychological characteristics that cannot be directly observed.
Operational definitions are the procedures we use to measure anything.
4 types of forces:
- The strong force – The electromagnetic force
- The weak force – Gravity
All invisible, but they have effects. Many fields thus use some unobservable things.
Psychological Tests: Definition and Types
What is a psychological test?
Cronbach a systematic procedure for comparing the behavior of people. 3 components:
1. They involve behavioral samples
2. These samples must be collected in some systematic way
3. The purpose is to compare the behavior of people
Features:
- Generality – many forms – for many kinds of information
- General purpose
Interindividual differences OR intraindividual differences
Types of Tests
Test can vary in content, for different kinds of information.
Tests can vary with regard to the type of responses – open-ended, multiple choice.
Tests can vary with regard to the intended purpose of the scores.
- Criterion referenced (domain referenced)
Usually when it’s for someone’s skill level, to sort people in 2 groups
- Norm referenced
To compare a person to other people from a reference sample / normative sample.
Sample of people who complete a test and they are representative.
Another distinction is between speeded tests and power tests.
- Speed – knowledge
, Test Theory
Psychometrics
What Is Psychometrics?
Focus on the evaluation of the attributes of tests. 3 most important ones:
- Type of information (sometimes, scores)
- Reliability of data
- Issues concerning the validity of data
A Brief History of Psychometrics
2 key foundations:
The practice of psychological testing and measurement.
The development of particular statistical concepts and procedures.
Psychometrics as a scientific discipline, is relatively young, but has enjoyed a quick evolution
and widespread application.
Challenges to Measurement in Psychology
All measurements and all sciences are affected by various challenges that can reduce
measurement accuracy.
Measurement in the behavioral sciences has unique challenges.
- Complexity of psychological phenomena
We need to identify and capture the important aspects of these attributes
- Participant reactivity
The knowledge of being measured can influence one’s state. Different kinds:
o Demand characteristics
Changing behavior to accommodate the researcher
o Social desirability
o Malingering
- Those collecting the data can bring biases and expectations
Also happens in physical sciences, but less
- Psychologists rely on composite scores
Benefits and issues
- Score sensitivity
The ability to discriminate between meaningful units of the dimension
- Lack of awareness of important psychometric info
Although measurement in the behavioral sciences and measurement in the physical
sciences have much in common, there are important differences. These should always
inform our understanding of collected data.
The Importance of Individual Differences
One person’s score can (best) be understood in comparison with others.
We need behavioral samples.
Psychometrics Goes Well Beyond “Differential” Psychology
Psychometrics is not limited to issues in differential psychology.
, Test Theory
Chapter 2 Scaling
Psychological measurement is a process through which numbers are assigned to represent
the quantities of psychological attributes.
Stevens proposed the most used definition of ‘measurement’ and the scales of
measurement.
Scaling is the way numerical values are assigned to psychological attributes.
Fundamental Issues With Numbers
Numerals are used to represent one’s level of a (psychological) attribute.
3 important properties of numerals and the meaning of 0
The Property of Identity
Most fundamental. Those within a category should be the same as each other in terms of
sharing a psychological feature, but they should be different from those in another category.
Rules for sorting people into categories:
1. To establish a category, the people within a category must satisfy the property of
identity.
2. The categories must be mutually exclusive.
3. The categories must be exhaustive; it should be ‘easy’ to put someone in one of the
categories.
At this levels, the numerals don’t have any mathematical value. They point out differences in
quality, not in amount. This property is pretty shallow. So, there are more:
The Property of Order
This one conveys greater info, about the relative amount of an attribute that people have.
This has to do with rank order. The numerals still only serve as a label, but this time in order.
The Property of Quantity
When numerals have this property, they can provide info about the magnitude of differences
between people. So, the numerals do have a mathematical value. They are real numbers:
- Standardized quantities
- Continuous
The Number 0
2 possible meanings:
1. Zero reflects a state in which an attribute of an object or event has no existence.
Absolute zero
2. It is an arbitrary quantity of an attribute.
Relative/ arbitrary zero.
Sometimes hard to decide which zero you’ve got. But, to interpret a test or its scores
correctly, it’s important which zero they use.
Units of Measurement
For the property of quantity, the units of measurement need to be defined and these units
need to be countable. Easy with length, not as easy with a psychological characteristic.
3 ways in which a measurement unit might be arbitrary:
1. The unit size can be arbitrary
The specific size of a unit might be arbitrary; chosen by you
2. Some units of measurement aren’t tied to any one type of object
There might be no inherent restriction on the objects to which a unit of measurement
might be applied.
3. Some units can be used to measure different features of objects, looking at physical
form. The unit measurement might be useable for length, but maybe also for weight?
Units of measurement = standard measures, are based on arbitrary units of measurement in
all 3 ways, when they take a physical form. However, when they take a psychological form,
they are usually only arbitrary in the first sense of the term.
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