Chapter 3: Variables, Reliability and Validity Flashcards
What are variables and how should they be defined?
They can be qualitative/categorical or quantitative, be discrete or continuous, be measured or manipulated or controlled or allowed to vary randomly. All variables in research must be operationally defined.
What is an operational definition?
An operational definition of a variable is a definition in terms of the exact operations required to measure or manipulate it; an example with memory is the number of studied words that were recognized
What is identity as a property of measurement?
A variable has the property when things that are different have different scores, values, or labels
What is magnitude as a property of measurement?
A variable has this property when the order of the scores, values, or labels reflects the ordering of the values on the variable
What is equal unit size as a property of measurement?
A variable has this property when a difference of any given size is the same throughout the range of possible values of the variable
What is absolute zero as a property of measurement?
A variable has this property when a score of 0 indicates a complete absence of the variable being measured
What properties does a nominal scale have? Define nominal.
Identity/different labels refer to different levels of the variable example: zip codes, 1=female 2=male
What properties does an ordinal scale have? Define ordinal.
Identity and Magnitude/different labels refer to different values of the variable and only conveys ordering or ranking example: height, course grade, year in school
What properties does an interval scale have? Define interval.
Identity, Magnitude, and Equal Unit Size/different labels refer to different values, conveys both ordering and size of the difference between successive values example: temperature, direction measured in degrees
What properties does a ratio scale have? Define ratio.
Identity, magnitude, equal unit size, and absolute zero/can multiply and divide data. Different labels refer to different values, numbers are used to identify the values, the numbers convey both ordering and the size of the difference between successive values, and their is an absolute true zero example: percent correct on a test, response time, stimulus presentation time
What are the mathematical operations that can be performed on the different scales of measurement? (NOIR)
Nominal- count the values and calculate mode, Ordinal- greater or less than, count and rank, calculate mode and median, Interval- add and subtract the values, calculate mode median mean, Ratio- all of above as well as multiply and divide
What is a Qualitative Variable?
Refers to variables that are categorical (nominal or ordinal). Is discrete data.
What is a Quantitative Variable?
Refers to variables that are identified by numbers that mean something in terms of the values (interval or ratio). If values refer to whole numbers they are discrete and if values fall on a continuum they are continuous.
Reliability test: Test/Retest
Performance on an instrument (test, survey) on two separate occasions
Reliability test: Alternative-Forms
Performance on two instruments (test, survey) believed to measure the same thing
