Variables Flashcards
Variables
- characteristics that vary
- represent a concept
- can have more than one value or level
Independent Variable
- factor or predictor
- in intervention studies it is the presumed cause of (or influence upon) a measured effect
- variable that is manipulated
- in predictive validity and prognosis studies it’s the variable that’s presumed to predict an outcome of interest
- level=the number of forms or values the independent variable takes in a study
- when there is 1 factor or IV in a study it is considered a single factor design
Dependen Variable
- outcome of interest
- the variable that is hypothesized to be caused (or predicted) by the independent variable
Extraneous Variable
- confounds relationship between independent and dependent variable
- need to be anticipated and controlled for if possible
Discrete
- can assume only distinct values
- dichotomous (one of two values) or polytomous (1 of many distinct values)
Continuous
-theoretically can assume infinitely finer degrees of measurement depending upon the instrument utilized
Single Factor Experimental Design
- 1 IV
- X, O notation used to describe designs
- 4 types we reviewed: pretest, posttest control group design, post test only control group design, time series design, non-equivalent groups pre-post test control
Pre-test, Post-test, Control Group, One-Way Design
- factor=IV
- what is the effect of dynamic balance training on single leg stance time?
- population from which you draw a representative sample
- randomly assign sample into 2 groups: experimental and control
- measure baseline single leg stance time (O1)
- provide dynamic balance intervention to sample
- measure baseline single leg stance time (O2)
- 1 IV=dynamic balance training
- 1 DV=single leg stance time
- this is true experimental design
Post-test Only Control Group, One-Way Factorial Design
- what is effect of dynamic balance training on single leg stance time?
- population from which you draw a representative sample
- random assignment into control or experimental group
- provide dynamic balance intervention to experimental group
- measure single leg stance time (O1)
- one-way factorial design
- 1 IV=dynamic balance training
- 1 DV=single leg stance time
Time Series Design
- single group
- repeated measures over time
- before and after experimental intervention
Non-Equivalent Groups Pre-Post Test Control
-non-equivalent control group design
-naturally occurring groups: gender, age, cohort
-baseline characteristics unlikely to be equal between groups
-effect of multimedia learning on orthopaedic foundation test scores of 1st and 2nd year DPT students
N O1 X O2
N O1 O2
One Group, Pre-Test, Post-Test, One-Way Repeated Measures Design
- what is effect of dynamic balance training on single leg stance time?
- population from which you draw a representative sample
- measure baseline single leg stance time (O1)
- provide dynamic balance intervention to sample
- measure baseline single leg stance time (O2)
- O1 X O2
- repeated measures
One-Way Repeated Measures Design
- what is effect of cane placement on hip muscle activity in individuals with hip pain
- population from which you draw a representative sample
- measure baseline hip activity (O1)
- provide cane on contralateral side (X)
- measure hip activity (O2)
- move cane to ipsilateral side (X2)
- measure hip activity (O3)
Controlling for Order Effects in One-Way Repeated Measures Design
- randomize order that the levels of independent variable are presented to each subject
- use a cross over design
- 2 levels for IV cane placement (ipsilateral and contralateral side)
- divide sample in half
- one group begins with cane in CL side, one IL side
Factorial Design
- more than 1 IV
- each IV has 2+ levels
- 2 IV: two-way factorial design
- decide if each factor is a between groups or within groups factor
