Variables and Their Measurement Flashcards
Variable (definition)
Characteristic of an individual, object, or environmental conditoin
Types Of Variables (3)
1) Independent Variable
2) Dependent Variable
3) Extraneous Variable
Independent Variable (def)
The variable that is intentionally manipulated by researchers to produce a change in an outcome; there are levels indicated by the number of IV’s in the study
IV’s are used in ___ Types of studies (2)
- Interventional
- Prognostic
IV’s are NOT used in ___ Studies (1)
Descriptive; bc researchers don’t manipulate anything and there is no outcome of interest
Purpose of IV’s in Interventional Studies (2)
- Can draw CAUSE AND EFFECT relationships because manipulating an IV
- They are commonly used as treatments/interventions
Levels of IV’s (3)
- > 1 IV = factorial design
- 2x2 factorial design
- 2x3 factorial design
2x2 factorial design?
Means there are 2 IV’s with 2 levels
2x3 factorial design?
Means there are 2 IV’s with 3 levels
IV Prognostic Studies (3)
- CANNOT draw Cause and Effect relationships bc not manipulating anything!
- IV’s are used to predict the outcome of interest
- Not intentionally manipulated by researchers
Dependent Variable (def)
The outcome of interest
Purpose of IV’s and DV’s in Interventional Studies
-Manipulate IV to cause a change in the DV= CAUSAL relationship!
IV’s and DV’s in Prognostic Studies
-Assess whether the IV is associated with the DV or predicts the DV; looks at IV and tries to predict the DV
Extraneous Variable(def)
- An outside variable that influences the DV, but it’s not an IV- want to limit these!
- Should be controlled through study design and statistical adjustment so you can say without a doubt that change was from your tx
Discrete Variable (def)
Values are distinct categories
Dichotomous Variable (def)
- A type of discrete variable
- Variables who only have 2 possible values; ex. Male and Female
Continous Variable (def)
Variables who have a theoretical infinite number of values
Levels of Measurement (4)
1) Nominal
2) Ordinal
3) Interval
4) Ratio
Nominal Level of Measurement
- Includes values that are named CATEGORIES
- NO rank; no one category is better than another
- Statistical analysis uses FREQUENCIES (not means)
Ordinal Level of Measurement
- Categories have a RANK order relative to one another; some form of hierarchy (ex. Likert scales)
- Statistical Analysis uses FREQUENCIES (not means)
Interval Level of Measurement
- Assigns quantitative values to variables
- Do NOT have a KNOWN ZERO POINT, but zero doesn’t mean there is an “absence” of the characteristic
- Possible values extend to infinity and can be both positive or negative
- Values may be added and subtracted, but not multiplied or divided
Ratio Level of Measurement
- Have a RANK order, and a KNOWN ZERO POINT
- No negative values
- has a TRUE zero
- Values can be added, subtracted, multiplied, and divided
True zero (def)
If there is a zero present, there is an ABSENCE of the characteristic
What type of variable is MMT grades? Why?
Discrete and ordinal variable; not an infinite number of possibilities and there is a heirarchy
What type of variable is gender? Why?
Discrete (dichotomist) and Nominal variable; bc not an infinite number of possibilities and equal groups (no hierarchy)
What type of variable is Blood Pressure? Why?
Ratio Variable- bc there is a true zero (no negative numbers)
