Chapter 4 Flashcards
What is measurement?
Measurement Is the assignment of scores to individuals so that the scores represent some characteristic of the individuals.
What is psychometrics?
A subfield of psychology concerned with the theories and techniques of psychological measurement.
One thing to keep in mind about measurement:
The important point here is that measurement does not require any particular instruments or procedures. What it does require is some systematic procedure for assigning scores to individuals or objects so that those scores represent the characteristic of interest.
What is a construct?
Psychological variables that represent an individual’s mental state or experience, often not directly observable, such as personality traits, emotional states, attitudes, and abilities.
Why can’t psychological constructs be observed directly?
They represent tendencies to think feel or act in certain ways.
What are the BIG 5?
A set of five broad dimensions that capture much of the variation in human personality. Each of the big five can even be defined in terms of six more specific constructs called “facets” (Costa & McCrae, 1992).
BIG 5
Openness to Experience
Conscientiousness
Extroversion
Agreeableness
Neuroticism
What is a conceptual definition?
Describes the behaviors and internal processes that make up a psychological construct, along with how it relates to other variables.
What is an operational definition?
A definition of the variable in terms of precisely how it is to be measured.
What are the 3 categories of operational definitions?
Self-report measures: Measures in which participants report on their own thoughts, feelings, and actions.
Behavior measures: Measures in which some other aspect of participants’ behavior is observed and recorded.
Physiological measures: Measures that involve recording any of a wide variety of physiological processes, including heart rate and blood pressure, galvanic skin response, hormone levels, and electrical activity and blood flow in the brain.
What are converging operations?
When psychologists use multiple operational definitions of the same construct—either within a study or across studies.
Who suggested 4 scales of measurement?
The psychologist S. S. 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).
Stevens actually suggested four different levels of measurement (which he called “scales of measurement”) that correspond to four types of information that can be communicated by a set of scores, and the statistical procedures that can be used with the information.
What are the 4 levels of measurement?
Nominal
Ordinal
Interval
Ratio
Nominal Level of Measurement:
A measurement used for categorical variables and involves assigning scores that are category labels.
The essential point about nominal scales is that they do not imply any ordering among the responses. For example, when classifying people according to their favorite color, there is no sense in which green is placed “ahead of” blue. Responses are merely categorized. Nominal scales thus embody the lowest level of measurement.
Ordinal Level of Measurement
Pro: The ordinal level of measurement involves assigning scores so that they represent the rank order of the individuals.
Con: On the other hand, ordinal scales fail to capture important information that will be present in 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 like you cannot assume that the gap between the runners in first and second place is equal to the gap between the runners in second and third place).
Statisticians express this point by saying that the differences between adjacent scale values do not necessarily represent equal intervals on the underlying scale giving rise to the measurements.
Interval Level of Measurement
Pro: A measurement that involves assigning scores using numerical scales in which intervals have the same interpretation throughout.
Con: Interval scales are not perfect, however. In particular, they do not have a true zero point even if one of the scaled values happens to carry the name “zero.” The Fahrenheit scale illustrates the issue. Zero degrees Fahrenheit does not represent the complete absence of temperature (the absence of any molecular kinetic energy). In reality, the label “zero” is applied to its temperature for quite accidental reasons connected to the history of temperature measurement. Since an interval scale has no true zero point, it does not make sense to compute ratios of temperatures.
Ratio level of Measurement
A measurement that involves assigning scores in such a way that there is a true zero point that represents the complete absence of the quantity.
Pro: You can think of a ratio scale as the three earlier scales rolled up in 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 (in terms of the ordering of the numbers). 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 carries the same meaning
How do psychologists make sure their measures work?
Psychologists do not simply assume that their measures work. Instead, they collect data to demonstrate that they work. If their research does not demonstrate that a measure works, they stop using it.
What is reliability?
Reliability refers to the consistency of a measure. Psychologists consider three types of consistency: over time (test-retest reliability), across items (internal consistency), and across different researchers (inter-rater reliability).
What is test-retest reliability?
When researchers measure a construct that they assume to be consistent across time, then the scores they obtain should also be consistent across time. In general, a test-retest correlation of +.80 or greater is considered to indicate good reliability.
Again, high test-retest correlations make sense when the construct being measured is assumed to be consistent over time. . .But other constructs are not assumed to be stable over time.
What is internal consistency?
The consistency of people’s responses across the items on a multiple-item measure.
What is split-half correlation?
A score that is derived by splitting the items into two sets and examining the relationship between the two sets of scores in order to assess the internal consistency of a measure.
What is Cronbach’s alpha?
Perhaps the most common measure of internal consistency used by researchers in psychology is a statistic called Cronbach’s α (the Greek letter alpha). Conceptually, α is the mean of all possible split-half correlations for a set of items.
What is inter-rater reliability?
The extent to which different observers are consistent in their judgments. Interrater reliability is often assessed using Cronbach’s α when the judgments are quantitative or an analogous statistic called Cohen’s κ (the Greek letter kappa) when they are categorical.
What is validity?
The extent to which the scores from a measure represent the variable they are intended to.
When a measure has good test-retest reliability and internal consistency, researchers should be more confident that the scores represent what they are supposed to. There has to be more to it, however, because a measure can be extremely reliable but have no validity whatsoever.
There are three basic kinds: face validity, content validity, and criterion validity.
Think of validity as another type of evidence.
What is face validity?
The extent to which a measurement method appears, on superficial examination, to measure the construct of interest.
It can be assessed quantitatively but it is usually assessed informally.
Face validity is at best a very weak kind of evidence that a measurement method is measuring what it is supposed to.
What is content validity?
The extent to which a measure reflects all aspects of the construct of interest.
Like face validity, content validity is not usually assessed quantitatively. Instead, it is assessed by carefully checking the measurement method against the conceptual definition of the construct.
What is criterion validity?
The extent to which people’s scores on a measure are correlated with other variables (known as criteria) that one would expect them to be correlated with.
What is a criterion?
A variable that theoretically should be correlated with the construct being measured (plural: criteria).
What is concurrent validity?
A form of criterion validity, where the criterion is measured at the same time (concurrently) as the construct.
What is predictive validity?
A form of validity whereby the criterion is measured at some point in the future (after the construct has been measured), to determine that the construct “predicts” the criterion.
What is convergent validity?
A form of criterion validity whereby new measures are correlated with existing established measures of the same construct.
4 steps of measurement process:
Broadly speaking, there are four steps in the measurement process: (a) conceptually defining the construct, (b) operationally defining the construct, (c) implementing the measure, and (d) evaluating the measure.
Steps to operationalize a variable:
Use an existing measure
Among the advantages are that (a) you save the time and trouble of creating your own, (b) there is already some evidence that the measure is valid (if it has been used successfully), and (c) your results can more easily be compared with and combined with previous results. In fact, if there already exists a reliable and valid measure of a construct, other researchers might expect you to use it unless you have a good and clearly stated reason for not doing so.
Create your own measure:
-Strive for simplicity and brevity.
-Most measures are variations of pre-existing measures.
-Keep in mind that it is almost always better for a measure to include multiple items rather than a single item.
-Use your scale to test several people for troubleshooting purposes.
What are demand characteristics?
Subtle cues that reveal to participants how the researcher expects them to respond in the experiment.
Safeguards against influencing the participants in your study
There are several precautions you can take to minimize these kinds of reactivity. One is to make the procedure as clear and brief as possible so that participants are not tempted to vent their frustrations on your results. Another is to guarantee participants’ anonymity and make clear to them that you are doing so. If you are testing them in groups, be sure that they are seated far enough apart that they cannot see each other’s responses. Give them all the same type of writing implement so that they cannot be identified by, for example, the pink glitter pen that they used. You can even allow them to seal completed questionnaires into individual envelopes or put them into a drop box where they immediately become mixed with others’ questionnaires. Although informed consent requires telling participants what they will be doing, it does not require revealing your hypothesis or other information that might suggest to participants how you expect them to respond. A questionnaire designed to measure financial responsibility need not be titled “Are You Financially Responsible?” It could be titled “Money Questionnaire” or have no title at all. Finally, the effects of your expectations can be minimized by arranging to have the measure administered by a helper who is “blind” or unaware of its intent or of any hypothesis being tested. Regardless of whether this is possible, you should standardize all interactions between researchers and participants—for example, by always reading the same set of instructions word for word
