Measurement is the assignment of scores to individuals so that they represent some characteristic of them. This very general definition is consistent with the types of measurement with which everyone is familiar. For example, weighing yourself by getting on a bathroom scale or checking the internal temperature of a dish by inserting a meat thermometer. In this article we will provide you the information about the Levels of measurement in psychology.
It is also consistent with measurement in other sciences. In physics, for example, you can measure the potential energy of an object in the Earth’s gravitational field by finding its mass and height (which, of course, requires measuring those variables) and multiplying them by the Earth’s gravitational acceleration ( 9.8m/s2). The result of this procedure is a score that represents the potential energy of the object.
Measurement in Psychology
The general definition of measurement given is also consistent with measurement in psychology. For example, a cognitive psychologist wants to measure a person’s working memory capacity, that is, their ability to hold in mind and think about several pieces of information at the same time. To do this, he could use a backward digit span task, in which he reads a list of two digits to the person and asks him to repeat them in reverse order.
The operation is then repeated several times, increasing the length of the list by one digit each time, until the person makes a mistake. The length of the longest list to which the person responds correctly is the score and represents the person’s working memory capacity. Imagine that a clinical psychologist is interested in the degree of depression of a person. He administers the Beck Depression Inventory, which is a 21-item self-report questionnaire in which the person rates the degree to which they have felt sad, lost energy, and experienced other symptoms of depression in the past two weeks. The sum of these 21 ratings is the score and represents her current level of depression.
The important point here is that the measurement does not require any particular instrument or procedure. It doesn’t require placing people or objects on bathroom scales, holding rulers over them, or inserting thermometers. What it does require is some systematic procedure for assigning scores to individuals or objects so that those scores represent the characteristic of interest.
Variables Studied by Psychologists
Many of the variables studied by psychologists are straightforward and easy to measure. These include gender, age, height, weight, and birth order. You can often tell if someone is male or female just by looking at them. You can ask people how old they are and be reasonably sure they know and they will tell you. Even if people don’t know or don’t want to tell you how much they weigh, you can get them on a bathroom scale.
Other variables studied by psychologists are not as direct or simple to measure. We can’t accurately assess people’s level of intelligence by looking at them, and we certainly can’t put their self-esteem on a bathroom scale. These kinds of variables are called constructs and include personality traits (for example, extraversion), emotional states (for example, fear), attitudes (for example, toward taxes), and abilities (for example, athletics).
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psychological constructs
Psychological constructs cannot be directly observed. One reason is that they often represent tendencies to think, feel, or act in certain ways. For example, saying that a certain college student is very extraverted does not necessarily mean that she is behaving extraverted at the moment. In fact, she may be sitting quietly reading a book.
Instead, it means that you have a general tendency to behave extravertedly (talking, laughing, etc.) in various situations. Another reason psychological constructs cannot be directly observed is that they often involve internal processes. Fear, for example, involves the activation of certain structures of the central and peripheral nervous system. This is contrasted with certain kinds of thoughts, feelings, and behaviors, none of which are necessarily obvious to an outside observer. Note also that neither extraversion nor fear is reducible to any particular thought, feeling, act, or physiological structure or process. On the contrary, each of them is a kind of summary of a complex set of behaviors and internal processes.
Concept Definition
The conceptual definition of a psychological construct describes the behaviors and internal processes that make it up, along with their relationship to other variables. For example, a conceptual definition of neuroticism would be that it is the tendency for people to experience negative emotions such as anxiety, anger, and sadness in various situations. This definition could also include having a strong genetic component. It remains fairly stable over time and is positively correlated with the tendency to experience pain and other physical symptoms.
Students sometimes wonder why, when researchers want to understand a construct like self-esteem or neuroticism, they don’t just look it up in the dictionary. One reason is that many scientific constructs have no equivalents in everyday language (for example, working memory capacity). More importantly, researchers are working to come up with definitions that are more detailed and precise—and that more accurately describe the way the world is—than informal dictionary definitions.
As we shall see, they do so by proposing conceptual definitions, testing them empirically, and revising them if necessary. Sometimes they rule them out entirely. That is why the research literature often includes different conceptual definitions of the same construct. In some cases, an old conceptual definition has been superseded by a new one that fits and works better. In others, researchers are still deciding which of several conceptual definitions is the best.
Operational definitions
An operational definition is a definition of a variable in terms of exactly how it should be measured. These measures generally fall into one of three broad categories. Self-report measures are those in which participants report their own thoughts, feelings, and actions, such as the Rosenberg self-esteem scale.
For any variable or construct, there will be multiple working definitions. Stress is a good example. A rough conceptual definition is that stress is an adaptive response to perceived danger or threat. It involves physiological, cognitive, affective and behavioral components. But researchers have defined it operationally in various ways. The Social Readjustment Rating Scale is a self-report questionnaire. In this case, people identify the stressful events they have experienced in the past year and assign points to each based on their severity.
For example, a man who has been divorced (73 points), changed jobs (36 points), and had a change in his sleeping habits (16 points) in the last year would have a total score of 125. The Scale of Everyday Trouble and Lift is similar, but focuses on everyday stressors like misplaced items and weight concerns. The Perceived Stress Scale is another self-report measure that focuses on people’s feelings of stress. Here we can take as an example How often have you felt nervous and stressed? Researchers have also operationally defined stress in terms of several physiological variables, such as blood pressure and levels of the stress hormone cortisol.
Behavior Measures
Behavioral measures are those in which some other aspect of the participants‘ behavior is observed and recorded. This is a very broad category that includes the observation of people’s behavior both in highly structured laboratory tasks and in more natural settings. A good example of the former would be the measurement of working memory capacity using the backward digit span task.
A good example of the latter is a famous operational definition of physical aggression by researcher Albert Bandura and his colleagues. They let each of several children play for 20 minutes in a room containing a clown-shaped punching bag called a Bobo doll. They filmed each child and counted the number of acts of physical aggression he committed.
These acts included hitting the doll with a mallet, punching and kicking it. Its operational definition, therefore, was the number of these specifically defined acts that the child committed during the 20-minute period. Finally, physiological measurements are those that involve recording a wide variety of physiological processes, such as heart rate and blood pressure, galvanic skin response, hormone levels, and electrical activity and blood flow in the brain. .
Converged Operations
When psychologists use multiple operational definitions of the same construct, either within a study or across studies, they are using convergent operations. The idea is that the different operational definitions converge or come together in the same construct. When scores based on several different operational definitions are closely related to each other and produce similar patterns of results, this is good evidence that the construct is being measured effectively and is useful.
The various measures of stress, for example, are all correlated with each other and have all been shown to be correlated with other variables such as immune system function. This is what allows researchers to eventually draw useful general conclusions. As an example we can point out that stress is negatively correlated with the functioning of the immune system. This is stated in contrast to more specific and less useful ones, such as people’s scores on the Perceived Stress Scale being negatively correlated with their white blood cell counts.
Measurement Levels
The psychologist SS Stevens suggested that scores can be assigned to individuals in ways that convey more or less quantitative information about the variable of interest. For example, officials in a 100-meter race could simply order the runners as they cross the finish line (first, second, etc.), or they could time each runner to the nearest tenth of a second using a stopwatch (11 .5s, 12.1s, etc.).
In either case, they would measure the runners’ times by systematically assigning scores that represent those times. However, while the qualifying procedure communicates the fact that the second runner took longer to finish than the first, the stopwatch procedure also communicates how long the second took. Actually, Stevens proposed four different levels of measurement which he called measurement scales. They correspond to four different levels of quantitative information that a set of scores can communicate. Below are the Levels of measurement in psychology.
Nominal Measurement Level
The nominal measurement level is used for categorical variables and involves the assignment of scores that are category labels. Category labels communicate whether two individuals are the same or different in terms of the variable being measured. For example, if you observe the research participants as they enter the room, decide whether each is male or female, and enter this information into a spreadsheet, you are performing a nominal level measurement.
Or if you ask participants to indicate which of the different ethnicities they identify with, you are also taking a nominal level measurement. The essential thing about nominal scales is that they do not imply any order among responses. For example, when ranking people by their favorite color, there is no sense in which green ranks ahead of blue. The responses are simply ranked. Therefore, the nominal scales represent the lowest level of measurement.
The remaining three measurement levels are used for quantitative variables. The ordinal level of measurement consists of assigning scores in a way that represents the rank order of individuals. Ranges communicate not only whether two individuals are the same or different in terms of the variable being measured. Here it is also measured whether an individual is higher or lower on that variable.
For example, a researcher wanting to measure consumers’ satisfaction with their microwave ovens might ask them to specify their feelings as “very dissatisfied,” “somewhat dissatisfied,” “somewhat satisfied,” or “very satisfied.” The items on this scale are ordered, ranging from least to most satisfied. This is what distinguishes ordinal from nominal scales.
Ordinal Measurement Level
Unlike nominal scales, ordinal scales allow us to compare the degree to which two individuals value the variable. For example, our ranking of satisfaction makes it meaningful to say that one person is more satisfied than another with their microwave oven. This statement reflects the first person’s use of a verbal label that appears later in the list than the label chosen by the second person.
On the other hand, ordinal scales do not capture important information that will be present at the other levels of measurement we examine. In particular, the difference between two levels of an ordinal scale cannot be assumed to be the same as the difference between two other levels. Just as the difference between the first and second place runners cannot be assumed to be equal to the difference between the second and third place runners.
On a satisfaction scale, for example, the difference between the responses “very dissatisfied” and “somewhat dissatisfied” is probably not equivalent to the difference between “somewhat dissatisfied” and “somewhat satisfied.” Nothing in our measurement procedure allows us to determine whether the two differences reflect the same difference in psychological satisfaction. Statisticians express this point by saying that differences between adjacent scale values do not necessarily represent equal intervals on the underlying scale giving rise to the measurements.
Interval Metering Level
The interval measurement level involves assigning scores using numerical scales. In this case, the intervals have the same interpretation at all times. As an example, consider the Fahrenheit or Celsius temperature scales. The difference between 30 and 40 degrees represents the same temperature difference as the difference between 80 and 90 degrees. This is because each interval of 10 degrees has the same physical meaning (in terms of the kinetic energy of the molecules).
However, interval scales are not perfect. In particular, they do not have a true zero point even if one of the scale values happens to be zero. The Fahrenheit scale illustrates the problem. Zero degrees Fahrenheit does not represent the complete absence of temperature (the absence of any molecular kinetic energy). Actually, the Zero label is applied to its temperature for rather accidental reasons related to the history of temperature measurement.
Since an interval scale does not have a true zero point, it makes no sense to calculate temperature relationships. For example, it doesn’t make sense that the ratio of 40 to 20 degrees Fahrenheit is the same as the ratio of 100 to 50 degrees. No interesting physical properties are preserved in the two relationships. After all, if the Zero label were applied to the temperature that Fahrenheit labels as 10 degrees, the two ratios would be 30 to 10 and 90 to 40 are no longer the same.
For this reason, it makes no sense to say that 80 degrees is twice as hot as 40 degrees. Such a statement would depend on an arbitrary decision about where to start the temperature scale. That is, what temperature to call Zero (while the statement is intended to make a more fundamental statement about the underlying physical reality). In psychology, intelligence quotient (IQ) is often considered to be measured at the interval level.
Ratio Measurement Level
Finally, the level of measurement of the proportion implies the assignment of scores. This is done so that there is a real Zero Point that represents the total absence of the quantity. Height measured in meters and weight measured in kilograms are good examples. So are counts of discrete objects or events, such as the number of siblings one has or the number of questions a student answers correctly on a test.
A ratio scale is like the previous three scales rolled into one. Like a nominal scale, it provides a name or category for each object (the numbers serve as labels). Like an ordinal scale, the objects are ordered (based on the order of the numbers). Finally, just like an interval scale, the same difference at two places on the scale has the same meaning. However, in addition, the same ratio at two places on the scale also has the same meaning.
We hope that you have understood the Levels of measurement in psychology.
