Introduction To Psychometrics and Psychological Measurements. A Psychological Statistics Podcast Episode.

Whilst statistics might be a psychological topic that lots of aspiring and qualified psychologists dread, learning about psychometrics and psychological measurements is a lot of fun and it is really interesting. We need to understand how to create good psychometric measurements so we can measure the behaviour we intend to and not any other variables. This is even more important for aspiring and qualified clinical psychologists where the quality and accuracy of our psychometric measurements could be the difference between people receiving or being denied mental health support. This statistics topic is critical to understand and appreciate. Therefore, in this psychological statistics podcast episode, you’ll learn what are psychometrics, what are psychological measurements and a lot more insightful facts that will deepen your understanding of statistics.

Today’s psychology podcast episode has been sponsored by 401 Statistics Questions For Psychology Students: A Guide To Psychology Statistics, Research Methods and More. Available from all major eBook retailers and you can order the paperback and hardback copies from Amazon, your local bookstore and local library, if you request it. Also available as an AI-narrated audiobook from selected audiobook platforms and library systems. For example, Kobo, Spotify, Barnes and Noble, Google Play, Overdrive, Baker and Taylor and Bibliotheca.

Psychometrics and Psychological Measurements

I think this is a great chapter to kick-off the deep-dive sections of the book because psychometrics and psychological measurements, are essentially the lifeblood of psychology as a science. Due to if we didn’t use psychometrics and if we didn’t have valid, reliable measures then psychology wouldn’t be a science and that would be awful.

Then again, this is an issue that no one normally thinks about, because I never think about psychometrics and measurements. And that’s slightly concerning because in clinical psychology we want to measure and track someone’s mental health condition with accuracy and reliability.

I’m hardly alone.

I don’t think I know too many applied or even theoretical psychologists who focus on psychometrics and psychological measurements. Leading us to use the same tools and scales over and over again without anyone truly focusing on how good they actually are.

This is the focus and aim of the various topics that we’re going to be looking at in this book.

What Is A Measurement In Psychology?

In statistics, a measurement is the assignment of numbers to a quantifiable attribute according to a rule. Also, this rule can be arbitrary so this allows for multiple assignments. For example, temperature can be measured in Fahrenheit or Celsius, which are two different scales/ assignments. As well as these two scales can be turned into each other because they have a linear transformation.

Equally, this assignment can be non-linear because the Richter scale is a way to measure earthquakes. Each number means the earthquake is 10 times more powerful than the previous number. Therefore, if an earthquake has a value of 10 on the Richter scale then it is 10 times more powerful than an earthquake that has a value of 9.

What Is Scaling In Psychology?

In statistics, scaling is the process of setting up the rule of correspondence between observations and numbers assigned. As well as McDonald (1999) added that data and observations are very different, because data are scaled observations.

What Are Noisy Measurements?

According to Henk Kelderman noisy measurements are outcomes that are considered indicators of a given attribute but these indicators cannot be directly observed.

What Are Some Examples of Noisy Observations?

Noisy observations can include non-response, recall, subjectivity, response styles and self-deception as well as motivated misresponse.

What Are Psychometrics?

In psychology statistics, psychometrics focuses on the development of formal methods and theories that help us to study the fidelity and appropriateness of different psychological measurements.

In addition, Dr Henk Kelderman writes at http://www.psychometrika.org/society/index.html):

“Measurement and quantification is ubiquitous in modern society. In early modernity, the scientific revolution provided a firm scientific basis for physical measures like temperature, pressure, and so on. In the late nineteenth and early twentieth century, a similar revolution took place in psychology with the measurement of intelligence and personality. A crucial role was played by Psychometrics, initially defined as "The art of imposing measurement and number upon operations of the mind.”

Since 1936 the Psychometric Society has been at the forefront of the development of formal theories and methods to study the appropriateness and fidelity of psychological measurements. Because measurement in psychology is often done with tests and questionnaires, it is rather imprecise and subject to error. Consequently, statistics plays a major role in psychometrics. For example, members of the society have devoted much attention to the development of statistical methods for the appraisal of noisy measurements whose outcomes are considered indicators of attributes of interest that cannot be directly observed.

Today, psychometrics covers virtually all statistical methods that are useful for the behavioral and social sciences including the handling of missing data, the combination of prior information with measured data, measurement obtained from special experiments, visualization of statistical outcomes, measurement that guarantees personal privacy, and so on. Psychometric models and methods now have a wide range of applicability in various disciplines such as education, industrial and organizational psychology, behavioral genetics, neuropsychology, clinical psychology, medicine, and even chemistry.”

What Are Some Ways To Collect Observations In Psychology?

To gather observations you could collect reaction times, self-reports, peer ratings, time to relapse, time in remission, basal level of skin conductance and many, many more.

What Is Theory of Data?

According to Coombs (1960), his Theory of Data classifies the essential focus of every psychological measurement we use in the discipline is to associate each construct of interest, stimulus or individual to a point in a psychological space. Also, he mentioned in his 1960 paper that “basically, all a person can do is to compare stimuli with each other, or against some absolute standard or personal reference point.”

How Many Categories Are Optimal For Likert Scaling?

Whilst it is technically true that more categories mean more data points, in reality, 5 categories are optimal in Likert Scaling. Since research shows participants cannot meaningfully differentiate between more than 7 categories.

What Is Another Name For Optimal Scaling?

Correspondence analysis is another name for optimal scaling.

What Is Optimal Scaling?

This type of scaling derives its values for response options that are statistically optimal. For example, Optimal Scaling seeks to maximise the internal consistency of a scale (also known as the correlations between the stimuli measuring the same thing).

How Are Test Scores Assigned?

A test score in statistics is assigned using one of the scaling methods. As well as test score is the weighted sum of the item scores or it is the sum of the items scores. The weight of each item score is determined before scoring as well as optimal scaling and judgemental scaling assign their weights to basic responses.

What Is A Criterion-Referenced Measurement?

This is a measurement that is referenced by a pre-defined standard of behaviour (this is the criterion). Since the criterion is the area of a subject that the test is designed to measure. For example, a criterion for a diagnosis of social anxiety disorder might be a client must endorse 80% of items on a questionnaire. This is a criterion-referenced measurement because you don’t need to compare this client to anyone else, you only been to reference their scores to criterion.

What Is A Norm-Referenced Measurement?

This is when a measurement is based on the distribution of scores obtained from the population that the researchers interested in. This is basically the “norm” that everyone is compared against.

What Is Thurstone’s Law of Comparative Judgement?

His Law of Comparative Judgement from 1927 proposes that each stimulus must elicit a psychological value from a participant. As well as the respondents should choose the stimulus with the highest psychological value at the moment of comparison with these values being distributed normally in the population.

What Is An Example of Measurement By Fiat?

Likert scaling is an example of measurement by Fiat because researchers have arbitrarily decided how to assign numbers to a response so this assignment lacks any empirical justification.

What Are Some Examples of Measurement of Modelling?

Since measurement by modelling involves scores that are based on models for stimulus respondent behaviour, Guttman and Thurstonian scaling are good examples.

What Is Type 1 Data In Psychology Statistics?

Type 1 data or Type 1 Observations are preferential choices where the participant is asked which of the two stimuli they prefer.

What is Type 2 Data?

Type 2 data is Single Stimulus where participants are asked where they stand in relation to the stimulus.

What is Type 3 Data?

Type 3 Data is stimulus comparison where participants are asked which of the two stimuli have more of some attributes.

What Is Type 4 Data?

Type 4 Data is Similarities where participants are asked which of the two pairs of stimuli are more alike.

What Type of Data Is Used In Multidimensional Scaling?

Similarities (Type 4 Data) is used in Multidimensional scaling.

What Type Of Data Does Thurstonian Scaling Use?

Thurstonian Scaling works for both Type 1 Data (preferential choice) and stimulus comparison (Type 3 Data).

What Is Thurstonian Scaling?

In 1927, Thurstone proposed a way to estimate population means of stimuli from their rank orderings in a sample drawn from the population of interest. Therefore, all means can be estimated in relation to the mean of some “referent” stimulus if we follow some basic rules of comparative judgements which he called Thurstone’s Law of Comparative Judgements.

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Have a great day.

Statistical Psychology Reference

Whiteley, C. (2025) 401 Statistics Questions For Psychology Students: A Guide To Psychology Statistics, Research Methods and More. CGD Publishing. England.

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