An Introduction to Psychological Assessment and Psychometrics

Keith Coaley

• Publisher: SAGE Publications Ltd
• Year: 2014
• ISBN:
  9781473904309
• Edition: 2
• Topic: Psychology
• Subtopic: Research & Methodology in Psychology
• Index: Psychology

In An Introduction to Psychological Assessment and Psychometrics, Keith Coaley outlines the key ingredients of psychological assessment, providing case studies to illustrate their application, making it an ideal textbook for courses on psychometrics or psychological assessment. New to the Second Edition:

• Includes occupational and educational settings
• Coversethical and professional issues with astrong practical focus
• Case study material related to work selection settings
• End of chapter self-assessments to facilitate students' progress
• Compliant with the latest BPS Certificate of Testing curriculum

1

INTRODUCTION: INDIVIDUAL DIFFERENCES AND PSYCHOMETRICS

Learning Objectives

By the end of this chapter you should be able to:

• discuss the general ideas and approaches to understanding individual differences and how psychological assessment and psychometrics enable their investigation;

• understand the basic principles underlying psychological assessment and distinguish between its various forms;

• identify key figures in the historical development of psychometric testing;

• give an account of the core characteristics and issues relating to different approaches to testing.

WHAT IS THIS CHAPTER ABOUT?

Applied psychologists ply their trade in the real world of individual differences. We must begin by understanding the nature of these. We must also introduce the core definitions, characteristics and foundations underlying modern approaches to assessment and psychometrics. It helps also to have an understanding of the historical origins of modern test practice, so we will review their development, identifying those explorers who have had a significant and enduring influence. We will also look at key terms and issues, discuss common types of test and how they can be classified or grouped. We will also review how they contribute to the application of individual differences in different fields.

INDIVIDUAL DIFFERENCES, ASSESSMENT AND PSYCHOMETRIC TESTING

Many people come to the study of psychology because of a terrific fascination for others, not just people at large but also perhaps for specific groups, such as children, those having disabilities, older people, criminal offenders, etc. Perhaps you have chosen to read this book because you want to understand others more than you do now. Do you observe others? Do you wonder why they behave as they do? Do you often wonder why some people seem similar yet can be strikingly different in certain ways? Welcome to the discipline of psychology.

Perhaps you want to start by reading the theories that try to explain why people are the way they are. History has thrown up a number of these. There are those which classify different kinds of people in some way, some that try to investigate their emotions or behaviours, some that try to analyse personality, some that look at how people develop, others that try to link biology and behaviour, and many more. Theorists will often make assumptions about people which they link to the psychological ideas they have generated.

Many theories focus upon similarities. The trouble with this is that people can be quite similar in some ways but will also be different in others and so make understanding even more complex. Theories are all very good in themselves but their assumptions make it difficult to understand the ‘what and why?’ of differences. Attempts to understand need analysis and measurement of the differences between people.

This book is about methods for linking the theories to greater understanding of individual differences through scientific investigation and measurement. We can evaluate the theories and the similarities among people and we can also scientifically analyse and measure the differences. Hence the title, An Introduction to Psychological Assessment and Psychometrics. We can only evaluate the similarities and the differences between people through the use of modern forms of assessment and valid psychometric tests. In the twenty-first century the use of armchair observation has long gone. By reading this book you will learn about the theories and how to measure the differences.

The study of individual differences has grown over a long period, sometimes being called ‘differential psychology’. The importance of this was stressed by Anne Anastasi (1937) when she wrote ‘It is apparent that if we can explain satisfactorily why individuals react differently from each other, we shall understand why each individual reacts as he does’. To determine the unique characteristics of someone we need to both identify and quantify the differences with others. Social comparison theory suggests, in fact, that we learn how to define the self by comparing ourselves with others (Festinger, 1954).

Why Measure Individual Differences?

The benefits are enormous. Tests identify differences in a number of ways, for example in measuring different levels of clinical, forensic, educational or neuropsychological problems, as well as in helping commercial organizations to select or develop their people. In their classic (1997) text Anastasi and Urbina point to their significant role in basic research: for example, studies on the nature and extent of individual differences; the organization of psychological traits; the measurement of group differences; and the identification of biological and cultural factors associated with behavioural differences. Reliable and valid tests provide the principal scientific approach to the measurement of differences between people.

Let’s look at this in a practical way. If you want to assess somebody, for what purpose would you wish to do so? You might want to discover, for example, whether that person can stay calm in a crisis or is confident in social situations, or whether he or she is anxious or depressed. Perhaps you want to say: ‘Yes, John is calm in a crisis’ or ‘June is socially confident’. Similarly, you might say: ‘John is anxious’ or ‘June is depressed’. Would those results then be good enough for you?

Take the example of calmness. Most people can be seen as calm to some extent. But could they all be 100% calm? And how would you know the difference? Many people appear to be socially confident, but isn’t it true that some are more confident than others? Aren’t there also people who have very low or high anxiety? A very anxious person might cover this up behind a smile. June might just be mildly depressed, while someone else is severely depressed. If your assessment doesn’t take account of the differences between people, then it doesn’t help you very much.

Over a long period psychological theories have tended to focus more on the similarities between individuals. In fact, according to Cooper (2002), much of psychology has been based upon the discovery of general rules describing behaviour, and as a result theories have been founded upon generalizations seeking to apply characteristics to all of us. The trouble with these kinds of theory is that they don’t take into account the fact that we may prefer to be different, or even odd, in the way we dress or behave in public. The ‘oddball’ celebrity, comedian or entertainer is probably a common sight on television. On the other hand, others will want to fit in with a crowd, though that crowd may have its own distinctive ways of dressing and behaving. They must be different from other groups. As we grow older we may tend to switch groups and be yet more different again. It seems that many people do prefer to be different.

Is it wrong then to apply generalizations to everybody? Well, it does appear that many people do have some things in common. Many psychological dimensions are, in fact, shared. But at the same time people tend to differ in how they portray or act out characteristics of them. We all develop through childhood in a fairly standard way, though some people develop faster than others and some react differently to developmental stages. Life choices can vary. We all have a brain and a physiology which are constructed in much the same way and we have a ‘personality’. But our choices in terms of, say, friends, life partners or careers can be very different. A simple way of representing this is to say that some theories, themes and ideas may be shared by everybody, but these also enable us to have differences.

To understand someone you need to be able to assess the differences with others, whether in terms of job performance, personality, intelligence, abilities, behaviour, cognition or any other aspect. In other words, researchers seek to understand and model how people differ. Maltby et al. (2007) and Cooper (1998) refer to this approach in terms of the development of a ‘structural model’. Researchers also want to identify the underlying reasons for individuality, the principal modes by which people differ from each other, and understand the psychological processes involved as well. The result is a deeper understanding involving the ‘why’, ‘where’ and ‘when’ of differences. This approach is described as constituting a process model which includes their causes and consequences.

What aspects of psychology are investigated? These include the study not just of personality and intelligence, which are obvious areas of interest, but also studies of abilities, moods, motivation, beliefs, relationship factors, the impact of culture, environment and genetics, physical traits, abnormality, gender and racial differences, psychopathology, religion, creativity, leadership, attitudes and interests. This list could go on for a lot longer, especially if we consider the many different studies of people at work.

Cooper (2002) provides four good reasons for investigating:

• Because they are of interest in their own right. The fact that some people are different from others is an intriguing issue in its own right.

• Because psychological tests are useful in applied psychology. The study of individual differences, he says, almost invariably leads to the development and publication of psychological tests. Measuring a wide range of characteristics can be of immense value to a broad spectrum of professionals and help both society and individuals.

• Because tests are useful ‘dependent variables’ in other branches of psychology. The development of reliable and valid tests can be of importance for experimental research, helping to ensure a sound validation of theories.

• Other branches of psychology can predict behaviour better when they consider individual differences. By taking these into account, statistical tests can become more sensitive and indicate, for example, what it is that influences the behaviour of patients undergoing therapy.

The reasons for investigating individual differences, however, become more significant when we look at their application. Differences develop early in life and become significant during childhood. Educational and child psychologists are interested in these differences, and in how and why they occur. For example, a child may demonstrate slower development in early years, whether in physical or cognitive terms. Investigation means their origins and nature can be better understood and result in improved support and care. When children go to school other differences may become noticeable, often in social and intellectual skills. One child may interact less well with others, being more withdrawn and reserved. A component of this might be the child’s level of self-esteem. Another child might be more aggressive. One child may show slower intellectual development, whilst another leaps ahead. Identifying and investigating the origins, development and outcomes of differences enables psychologists and teachers to help children.

The study of individual differences has also had a big impact on the world of business. For example, there are many ways in which individual job performance varies and many sub-components, or reasons why, this can vary, for example in understanding the nature of leadership (see Box 1.1 which discusses research into this). Literature in this field has sought to identify the underlying factors responsible for individual performance differences (Neal & Hesketh, 2001). Another, possibly linked, major area relates to differences between people in terms of job satisfaction. Workers who were most satisfied were found to be better adjusted emotionally than their less satisfied colleagues as long ago as 1935 (Judge et al., 2001).

BOX 1.1 Are Great Leaders Born or Made?

Investigations into individual differences can have a big impact on our understanding of people. For example, what makes a leader? I mean a really good one. The study of leadership has been littered with theories over many years. Lots of people have generated theories about it, including psychologists, management and business consultants, and even political pundits and armchair thinkers. Indeed, the whole concept is far more complex than people think it is.

The historical line of research has even been referred to as the ‘Great Man’ approach, largely as a result of an early belief that successful leaders inherit stable characteristics over their life-span (Judge et al., 2002, 2004). In other words, they were born leaders. This must also have assumed that all great leaders are male. Recent research has changed this by evaluating characteristics that are thought to be less stable over the life-span.

A research example will help you understand the impact of studying and measuring individual differences on such a difficult concept. It is borrowed from Hoffman et al. (2010) who systematically examined the magnitude of the relationship between leader effectiveness in organizations and 25 individual differences. Hoffman and his colleagues combined two approaches:

• Trait-like individual differences are founded on the assumption that inherited traits distinguish leaders from non-leaders. These are thought to have an indirect impact on leadership effectiveness. Examples would be the traits of extraversion and conscientiousness. They would be less changeable and therefore would also suggest that ‘great leaders are born not made’.

• State-like individual differences don’t assume that leadership characteristics are stable throughout the life-span and are thought to be more changeable. These might be viewed in terms of knowledge or skills and have a more direct impact on performance. The suggestion would be that, to some extent, ‘great leaders can be made’.

Hoffman et al. used a computer-based search to identify and combine studies of leadership, resulting in a total sample size of 146,851. The outcomes from the assessment and measurement of people were then subjected to a process called meta-analysis, which will be explained in a later chapter. It brings together findings from a large number of participants in a number of studies, making it possible to get a more accurate assessment of outcomes.

Their results reveale...