Examples of scales of measurement in psychology. Introduction to Measurement and Statistics 2019-01-11
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Understanding Psychological Measurement
Nominal Scales: This is the most limited type of measurement involving classification of data e. Numbers may be used to represent the variables but the numbers do not have numerical value or relationship: for example, a. The 1 rating assigned to May indicates that she has more potential but does not indicate how much more potential than Joe. So a questionnaire that included these kinds of items would have good face validity. It is very easy to compute incomplete or inappropriate statistical analysis of one's data. That is, the scale does not allow for the complete absence of the phenomenon being measured. In other words, we added up the responses and divided by the number of them.
Most physical measurements are ratio scales. Other examples of variables measured on an ordinal scale include difficulty hard, medium, easy and the order of finishing a race first place, second place, and so on. Like a nominal scale, it provides a name or category for each object the numbers serve as labels. Stevens suggested that scores can be assigned to individuals in a way that communicates more or less quantitative information about the variable of interest Stevens, 1946. An interval scale looks at variables where both the order and difference is meaningful, but the ratio of the units is not meaningful. Like an ordinal scale, the objects are ordered in terms of the ordering of the numbers.
But, just as often, we take a number like the amount of sugar in our food and use it to represent something abstract or intangible like how healthy or nutritious the food is. Finally, a ratio scale is made up of variables where the order, difference and ratio all matter. Hence the mode is black since its the most occurring colour of shoes. Opinion polls and television ratings systems represent other uses of inferential statistics. Validity Validity is the extent to which the scores from a measure represent the variable they are intended to. The distance between the ordered categories in ordinal scale variables i.
It is simply a sorting operation in which all individuals or units or answers can be placed in one category or another i. Such arguments would be based on the fact that such measures do not really meet the requirements of an interval scale, because it cannot be demonstrated that equal numerical differences at different points on the scale are comparable. Thus, 60 degree Fahrenheit or -10 degrees Fahrenheit represent interval data. Most measures of psychological constructs are not true interval scales, according to the strict definition. With a ratio scale, we also have a point where none of the scale exists; when a person is born his or her age is zero. This might lead to further research concerning job satisfaction on cardiac care units or higher pay for nurses working in this area of specialization. Then, a total score was obtained across all items in the set, and low scores were interpreted as indicating strong disapproval and high scores were interpreted as indicating strong approval.
Measurement models represent an unobservable construct by formally incorporating a measurement theory into the measurement process. The remaining three levels of measurement are used for quantitative variables. Most psychological data collected by instruments and tests, measuring and other abilities, are ordinal, although some theoreticians have argued they can be treated as interval or ratio scales. Feel more confident about the exam for this module next Monday! The performance levels and descriptors used in standardized state tests provide general information about how a test score relates to the content that the test is designed to measure. Presumably, if a person is willing to accept a certain association, he is willing to accept all those that precede it on the list those with lesser intensities , though this is not necessarily the case as some critics of this scale point out. Measurement scales refer to the types of information provided by numbers.
Researchers have also operationally defined stress in terms of several physiological variables including blood pressure and levels of the stress hormone cortisol. Usually, you will these statistics in something called the results section. An individual may respond 8 to this question and be in less pain than someone else who responded 5. A score of 22 means very little to a parent who does not have access to the test itself. The classic example of an interval scale is Celsius temperature because the difference between each value is the same. Although this measure would have extremely good test-retest reliability, it would have absolutely no validity. If you are in over your statistical head, it does not make sense to risk an entire project by attempting to compute the data analyses yourself.
The second student would be 16 points above the mean which would indicate an above average potential for educational activities. This involves splitting the items into two sets, such as the first and second halves of the items or the even- and odd-numbered items. How do you categorise this data? Every animal under study is in one of the two states and there is no animal that cannot be described by these two states. Individuals competing in a contest may be fortunate to achieve first, second, or third place. For example, subject-matter experts constructing a job knowledge test for firefighters may be asked to rate the importance of knowing how to use certain pieces of equipment e. Zero degrees Fahrenheit does not represent the complete absence of temperature the absence of any molecular kinetic energy. Other examples include counts of observations or occurrences, such as the number of aggressive or prosocial behaviors per hour, or the frequency of drug use in the past month.
4 Types of Scales Used in the Field of Measurement in Psychology
If you're measuring the height of two trees and tree A is 36 inches tall and tree B is 72 inches tall, you can accurately say that B is twice as tall as A. A commonly drawn distinction has been to view an attitude as a predisposition to act in a certain way and an opinion as a verbalization of the attitude. In each there is a concept of zero income, zero weight, etc. The Bogardus social distance scale was created by sociologist Emory S. Summary Measurement refers to the assignment of numbers in a meaningful way.
The other unobserved quantities in Figure are the error terms, in the circles, which also impact responses on the three items. Instead, they collect data to demonstrate that they work. Handbook of Parametric and Nonparametric Statistical Procedures Fourth ed. To do this, she might use a backward digit span task, in which she reads a list of two digits to the person and asks him or her to repeat them in reverse order. She assigns the one on the bottom a score of 1, the one on top of that a 2, and so on.
Fear, for example, involves the activation of certain central and peripheral nervous system structures, along with certain kinds of thoughts, feelings, and behaviours—none of which is necessarily obvious to an outside observer. Again, it does not make sense to add together first and second place in a race--one does not get third place. The vocabulary test mentioned above is one example. The first thing we would need to do is collect some data. The evidence needed was the presence of additive structure — a concept comprehensively treated by the German mathematician Hölder, 1901.
