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EPPP Stats Highlights
Formulas and definitions of nuanced concepts
25
Psychology
Post-Graduate
12/03/2015

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Term
Chi Square Terms goodness of fit
2 kinds
Definition
for nominal data
2 assumptions: 1) independence of observation, 2) mutually exclusive and exhaustive categories

tells whether observed frequencies match expected

cannot use with time series/repeated measures designs

single-sample (one variable) and multiple-sample (multiple variable) versions - number of variables INCLUDES IV and DV
Term
ANOVA
Definition
Tests whether means of several groups are different. extends t-test to more than 2 groups.
Uses the F-statistic. Significant when > 1

F-ratio = MSB/MSW = (Treatment + Error)/Error

use post-hoc tests to identify where the difference lies (X, Y, XY intxn)
- Scheffe, Tukey, Fischers
Term
single sample t-test
Definition
compares a single sample to a known population mean to see if sig diff
Term
two-way ANOVA
Definition
when have more than one continuous IV w/ on continuous DV

also called Factorial ANOVA

"it depends" - interaction effects when significant
Term
MANOVA
Definition
when have more than one DV (may or may not have more than one IV)
Term
correlation measure for curvilinear relationships
Definition
ETA (nonparametric)
Term
homoscedasticity vs. heteroscedasticity
Definition
homo - equal scatter around regression line

hetero - unequal scatter around regression line (one portion of group might be further away from line while another is clustered around it closely)
Term
multicollinearity
Definition
overlap in predictive value of different IVs - you dont want this
Term
types of data:
nominal
ordinal
interval
ratio
Definition
nominal - categories/names (nonparametric)
ordinal - rank order (nonparametric)
interval - equal distance between data points, e.g., temperature. No absolute zero (parametric)

ratio - equal distance between data points, can be add, sub, mult, divide. has an absolute zero(parametric).
Term
central limit theorem states
Definition
as sample size increase, distribution of scores become a normal curve
Term
Standard Error of the Mean
Definition
Standard deviation of the population mean --> tells error in your prediction of population mean from your sample. "the extent to which any one sample randomly drawn from the population can be expected to vary from the population mean...it is a measure of variability due to random error" calculated by dividing SD of population by square root of sample size (N)
Term
Maximize power by
Definition
increasing alpha
increasing sample size
decrease extraneous variables (control for or covary out)
increase ES (maximize intensity of IV)
1-tailed test
parametric test
Term
What are the nonparametric siblings of these tests?
t-test correlated groups
t-test independent sample
ANOVA
Definition
corr t-test = Wilcoxson Matched pairs

ind samp t-test = Mann Whitney U test

ANOVA - Kruskall-Wallis
Term
common assumptions of parametric and nonparametric, differences, and shortcomings
Definition
Common:
random selection of sample
independence of observations

Difference:
Parametric - normal distribution of data and homoscedasticity

Nonparametric tests are not as powerful
Term
pearson product coefficient
Definition
correlation coeff (r)

for interval or ratio data, tells straight up correlation
Term
Spearman Rank-Order (rho)
Definition
tells correlation of for ordinal or rank data
Term
Phi/point biserial
Definition
tells correlation of true dichotomy variable (sex)
Term
biserial
Definition
tells correlation of artificial dichotomy (high earners and low earners)
Term
contingency coefficient
Definition
tells correlation of NOMINAL data (e.g., DSM diagnosis)
Term
multiple regression
Definition
uses multiple continuous or discrete predictors to predict status on a continuous criterion variable.

gives a multiple correlation coefficient (R)

Types:
simultaneous - put all variables in at once
stepwise (add or subtract one variable at a time and see how R changes, stop when R-squared is high enough)
Term
cross validation
Definition
using a Mult Reg equation on a new sample. likely to get shrinkage of correlation coeff bc the same random error is not present in the second sample as in the first one
Term
discriminant function analysis
Definition
trying to predict an individual's status on a certain category/nominal criterion using 2 or more continuous predictors
Term
canonical correlation
Definition
extension of mult reg with 2 or more continuous predictors to predict status on 2 or more continuous criteria
Term
reject when true is not type II!
Definition
type 1 - reject a false null hypothesis (say there is an effect when there is not)
- determined by alpha

type II - retain a false null hypothesis (say there isnt an effect and there is)
- beta, cannot be known or controlled for. inverse relationship with alpha
Term
types of ANOVAs
Definition
• Multiple Analysis of variance (MANOVA)– used to control for Type I error
• Analysis of Covariance (ANCOVA)– using your statistical analysis to control for a compound variable
o Take out effect of a variable that is going to impact the study. (Ex.30 students in reading class, can take out a subject whose IQ will impact the testing)
• Randomized Blocked ANOVA (Block Design) – using a variable by classifying in your groups and in your study
o Three groups classified by reading aptitude (blocking part), want to improve reading aptitude (variable)
• Split-plot ANOVA – split design, works with between and within study.
o Mixed-design – within group and between group
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