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.
