Terminology and Statistics Flashcards
Between groups
looking at differences BETWEEN different groups
ex. Group 1 vs. Group 2
Within groups
-repeated measures
looking at differences WITHIN (same person over time)
ex. one participant: T1 vs T2 vs T3
Analysis of Variance (ANOVA)
- One- way = 1 IV
- Two-way = 2 IV
- Factorial = 2+ IV
F statistic
- Ratio of the variation explained by the model and the variation explained by unsystematic factors
- If an f statistic is 1 or greater, chances are it will be significant
The OVAs
ANOVA- analysis of variance
ANCOVA- analysis of covariance (1+ covariate)
MANOVA- multivariate analysis of variance ( 2+ DVs)
MANCOVA- multivariate analysis of variance (2+ DVs, 1+ covariate)
-Mixed- model design ANOVA
Mixed model design ANOVA
- gets its name because there are two types of variables involved, that is at least one between-subjects variable and at least one within-subjects variable.
- The mixed-design ANOVA model (also known as Split-plot ANOVA (SPANOVA)) tests for mean differences between two or more independent groups whilst subjecting participants to repeated measures. Thus, there is at least one between-subjects variable and at least one within-subjects variable.
Example of a mixed model design ANOVA
- For example, are there any differences amongst the heights of males and females at age 10 and age 20 years?
- Gender (male or female) is the between-subjects variable
- Age (10 or 20 years) is the within-subjects variable
- Of interest are the main effects for Gender and Age, and the Gender-Age interaction effect.
- This could be described as a 2 x (2) mixed-design ANOVA
Main effect
with example
- the overall effect of one independent variable.
- EXAMPLE: In an experiment in which both the type of psychotherapy (cognitive vs. behavioral) and the duration of psychotherapy (short vs. long) are independent variables, there is one main effect of type and another main effect of duration. The main effect of type is the difference between the average score for the cognitive group and the average score for the behavioral group … ignoring duration. That is, short-duration subjects and long-duration subjects are combined together in computing these averages. The main effect of duration is the difference between the average score for the short-duration group and the average score for the long-duration group … this time ignoring type. Cognitive-therapy subjects and behavioral-therapy subjects are combined together in computing these averages.
Interaction effects
with example
-In order to find an interaction, you must have a factorial design, in which the two (or more) independent variables are “crossed.” a special kind of effect that can be observed in factorial experiments. You have an interaction whenever the effect of one independent variable depends on the level of the other. This is actually a fairly easy idea.
Here are some examples. The combined effect of two or more variables, as demonstrated in a factorial design; interactions signify that the effect of one variable (e.g., sex of the subject) depends of the level of another variable (e.g., age)
- If cognitive psychotherapy is better than behavioral psychotherapy when the therapy is short but not when the therapy is long, then there is an interaction between type and duration of therapy.
- If the negative effect of noise level on concentration is greater for introverts than for extroverts, then there is an interaction between these two independent variables.
- If the boost in intelligence judgments due to smiling is greater for male stimulus persons than for female stimulus persons, then there is an interaction between smiling and sex.
- If drawing a smiley face on checks increases tips for female servers but not for male servers, then there is an interaction between drawing smiley faces (or not) and sex of the server.
crossover interaction
-the effect of one independent variable is not only different across levels of the second independent variable, it actually reverses. Imagine, for example, that introverts’ concentration levels started high and then dropped as the noise level increased, but extroverts’ concentration level started low and then increased as the noise level increased. This would be a crossover interaction.
Buzz words:
predictors =
relationship =
adjusting =
post-hoc =
regression
relationship
adjusting
three groups
Discriminant Function Analysis (DFA)
- quantitative variable to predict group membership (Categorical)
- reverse MANOVA
homoscedasticity (homogeneity of variance)
- Condition in which all the variable in a sequence have the same finite, or limited, variance
- When homogeneity of variance is determined to hold true for a statistical model, a simpler statistical or computational approach to analyzing data may be used due to a low level of uncertainty in the data
Two types of covariates:
mediator
moderator
moderator
a variable that INFLUENCES the strength of a relationship between two other variables
example: in arguments/debates, the two parties agree from the beginning to have a conversation. The moderator is simply there to help manage the strength of the two parties’ arguments. i.e., this variable has an effect for sure, but the relationship will be there one way or the other
mediator
a variable that EXPLAINS the relationships between two other variables
example:
- in disputes, mediators are usually called in when two parties are unable/willing to communicate. It all hinges on the mediator to help solve the problem. i.e., if the mediator is gone, the relationship is nonexistent!
Example of mediator vs moderator
-What’s the relationship between social class (SES) and frequency of breast self-exams (BSE)? Age might be a moderator variable, in that the relationship between SES and BSE could be stronger for older women and less strong or nonexistent for younger women. Education might be a mediator variable in that it explains why there is relation between SES and BSE. When you remove the effect of education, the relationship between SES and BSE disappears.
confounding variable
a variable that is influencing both the DV and IV and is not accounted for. Failure to account for confounding variables can lead to spurious relationship
Example: ice cream sales impact drowning deaths. This is a spurious relationship because it fails to account for season
covariate
a variable that has a relation with one or both of the IV and DVs, but does not appreciably change the relation between an IV and DV when included in a statistical analysis. Covariates are generally not of theoretical interest, but are often included in a model to explain additional variability in a DV
regression
used in prediction and forecasting
Types: linear, bivariate, logistic, quadratic, exponential, logarithmic, power, etc.)
bivariate regression
degree of relationship between two quantitative variables
logistic regression
degree of relationship between categorical variables
linear regression
when both the predictor and response variables are continuous and linearly related, so the response will increase or decrease at a constant ratio to the predictor. There can be more than one predictor
example of linear regression
As the number of farms has decreased in the U.S., the average size of the remaining farms has grown larger. Based on data (year and the corresponding average acreage/farm) predict the average acreage in 2000 and 2010 and determine which function gives the most realistic predictions