Final Flashcards
Bivariate correlation
an association that involves exactly two variables
Mean
the arithmetic average (use for categorical data, bar graph?)
T-Test
tests whether the difference between means (group averages) is statistically significant
Construct validity for association claims
How well was each variable measured?
Statistical validity for association claims
How well do the data support the conclusion?
Internal validity for association claims
Can we make a causal inference from association?
Correlation is NOT causation
External validity for association claims
To whom can the association be generalized?
Effect size
describes the strength of a relationship between two or more variables
- Larger effect sizes allow for more accurate predictions.
- Larger effect sizes are usually more important.
Statistical significance
refers to the conclusion a researcher reaches regarding the likelihood of getting a correlation of that size by chance.
Outlier
an extreme score; a single case or a few cases that stand out from the pack.
-Outliers matter the most when a sample is small.
Restriction of range
when the full range of scores for one of the variables in a correlational study is not provided.
-This can make the correlation appear smaller than it actually is.
Curvilinear association
when the relationship between two variables is not a straight line. It might be positive up to a point, and then become negative.
Three Causal Criteria
- Covariance of cause and effect
- Temporal precedence
- Internal validity
Covariance
results must show a correlation between the cause variable and the effect variable
Temporal precedence
the cause variable must precede the effect variable; it must come first in time
Internal validity
there must be no plausible alternative explanations for the relationship between the two variables
Directionality problem
we don’t know which variable came first (temporal precedence criterion)
Third-Variable Problem
When we come up with an alternative explanation for the association between two variables, that the alternative is some lurking third variable
(internal validity criterion)
Moderator
When the relationship between two variables changes depending on the level of another variable, that other variable is called a moderator.
Multivariate Designs
involve more than two measured variables
Longitudinal Design
can provide evidence for temporal precedence by measuring the same variables in the same people at several points in time
Cross-Sectional Correlations
Test to see whether two variables, measured at the same point in time, are correlated.
Autocorrelations
determine the correlation of one variable with itself, measured on two different occasions
Cross-lag correlations
show whether the earlier measure of one variable is associated with the later measure of the other variable. Three possible outcomes.
–Help to establish temporal precedence.
Multiple Regression
Using this technique, researchers can evaluate whether a relationship between two key variables still holds when they control for another variable. (can help rule out third variables)
Criterion variables
When researchers use multiple regression, the first step is to choose the variable they are most interested in understanding/ predicting
-Dependent variable
Predictor variables
The rest of the variables in a multiple regression analysis
-Independent variable
Beta Values
tell you the strength and direction of the relationship for multiple-regression analysis
Adding predictors to a regression
helps us:
- Control for several third variables at once.
- Get a sense for which predictors most strongly impact our criterion variable.
Does regression establish causation? Why or why not?
NO
- Doesn’t always establish temporal precedence.
- Can’t control for variables you don’t measure.
Parsimony
the degree to which a scientific theory provides the simplest explanation of some phenomenon. The simplest explanation of a pattern of data.
Mediator
mediating variable.
Can get at the why behind a relationship between variables
Experiment
when a researcher manipulates at least one variable and measured another
Manipulated Variable
a variable that is controlled, such as when researchers assign participants to a particular level of the variable
Measured Variable
take the form of records of behavior or attitudes such as self-reports, behavioral observations, or physiological measures
Independent Variable
the manipulated (causal) variable
Conditions
the IV’s levels
Dependent Variable
the measure or outcome variable
Control variable
any variable the experimenter holds constant on purpose. Trying to control for potential third variables.
Comparison group
Usually used when there is no control group. When the levels of the independent variable differ in some intended and meaningful way.
Control group
a level of an independent variable that is intended to represent “no treatment” or a neutral condition
Treatment group
the other levels of the independent variable that are not neutral make up the treatment group
Placebo group
when the control group is exposed to an inert treatment
Confounds
possible alternative explanations; potential threats to internal validity
Design Confound
an experimenter’s mistake in designing the independent variable. It is a second variable that happens to vary systematically along with the intended independent variable and therefore is an alternative explanation for the results.
Systematic variability
variability between groups that causes a confound
Unsystematic variability
random or haphazard variability - across both groups would NOT be a confound.
Selection effects
when the kinds of participants in one level of the independent variable are systematically different from those in the other. Can happen when experimenters let participants choose what group they want to be in.
Random assignment
helps us avoid selection effects
Matched groups
First measure the participants on a particular variable that might matter to the dependent variable. Next, they would match participants in pairs, and then randomly assign one of the two of them to each of the conditions.
Independent-groups design
different groups of participants are placed into different levels of the independent variable.
Within-groups design
there is only one group of participants and each person is presented with all levels of the independent variable.
Posttest only design
Participants are randomly assigned to independent variable groups and are tested on the dependent variable once.
-Satisfy all three criteria for a causal claim.
Pretest/posttest design
Participants are randomly assigned to at least two different groups and are tested on the key dependent variable twice - once before and once after exposure to the independent variable.
Within-groups design
there is only one group of participants and each person is presented with all levels of the independent variable.
Repeated-Measures Design
A type of within-groups design in which participants are measured on a dependent variable more than once, after exposure to each level of the independent variable.
Concurrent-Measures Design
A type of within-groups design where participants are exposed to all the levels of an independent variable at roughly the same time, and a single attitudinal or behavioral preference is the dependent variable.
Power
the probability that a study will show a statistically significant result when an independent variable truly has an effect in the population
Threats to internal validity in within groups design
- order effects
- practice effects
- carryover effects