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stats exam 3
stats exam 3
43
Psychology
Undergraduate 2
04/12/2011

Additional Psychology Flashcards

 


 

Cards

Term
correlation
Definition
the relationship between 2 variables. it tells us the magnitude and direction of the relationship through the correlation coefficient.
Term
most common correlation coefficient
Definition
pearson correlation coefficien
Term
equation of a straight line
Definition

y = a + bX

 

a= y intercept and b = slope

 

Term
4 reasons why correlation may or may not imply causation
Definition

1. X caused Y

2. Y caused X

3. The correlation between x and y was spurious

4. A third variable was responsible for the correlation between x and y

Term
three relevant questions about correlation
Definition

1. is there a relationship between the variables.

2. if so, whats the strength of the relationship?

3. whats the nature of the relationship?

Term

what numbers can the pearson correlation coefficient range from?

 

Definition

-1 to +1

 

0 means no correlation, -1 is perfect negative relationship, +1 is perfect positive relationship. Likelihood of finding a perfect or no relationship is very slim.

Term
how is magnitude determined?
Definition
how far the correlation coefficient is from 0
Term
regression
Definition
the prediction of one variable form one or more other variables
Term
regression formula
Definition

Y^= a + bX

 

a=slope of regression line

b= y intercept

Term
criterion variable
Definition
dependent variable, y, the variable thats being predicted
Term
predictor variable
Definition
independent variable, x, the variable from what predictions are made
Term
standard error of the estimate
Definition
amount of error when predicting y scores from x, also known as the residual
Term
curvilinear relationship
Definition
two things that are related but not linear
Term
range restriction
Definition
when you restrict a range of your sample data
Term
outliers
Definition
can cause a strong relationship to appear weak and vice versa
Term
standard error of the difference
Definition
The standard deviation of the sampling distribution of the difference between two independent means. It indicates how much sampling error will occur on average.
Term
standard error of the estimate
Definition
computing the standard error of the mean but taking into account degrees of freedom
Term
one sample t-test
Definition
needs to be used in place of a z score when the standard error of the mean is unknown
Term
independent groups t-test
Definition

used when

1. the dependent variable quantitative and measured on an interval level

2. the independent variable is between subjects in nature

3. the independent variable has 2 and only 2 levels

Term
the grand mean
Definition
the mean of the means
Term
treatment effects
Definition
when you subtract the grand mean from all of your other scores
Term

SSerror

 

Definition
amount of unexplained variability in the dependent variable, the variability that remains after the effects of the independent variable are removed
Term
Sstotal
Definition
the total variability in the dependent variable
Term
SSexplained
Definition
the amount of influence the independent variable had on the dependent variable
Term
eta squared
Definition
indexes the strength of the relationship between the IV and DV, proportion of variability in the DV that is associated with the IV
Term
weak, strong, average eta squared scores
Definition

.05= weak

.10 = average

.15 = strong

Term
correlated groups t-test
Definition

used when

1. the dependent variable is quantitative and is measured on an interval level

2. independent variable is WITHIN SUBJECTS in nature (why is why it differs from independent groups t-test)

3. the independent variable has 2 and only 2 levels

Term

advantages of correlated groups t-test:

 

Definition
controls for disturbance variables which makes it easier to detect a relationship, provides for a more sensitive test
Term
the most commong disturbance variable
Definition
individual difference
Term
sampling distribution of the mean of difference scores
Definition
theoretical distrubution consisiting of mean difference scores across all individuals in a sample for all possible random samples
Term
assumptions of the correlated groups t-test
Definition
the sample is independently and randomly selected, the population of difference scores is normally distributed, the dependent variable is quantitative in nature and measured on an interval level
Term
eta squared in a correlated groups t-test
Definition
the proporation of variability in the DV that associated with the IV after variability from individual differences has been removed
Term
downside of correlated groups t-test
Definition
since it is within subjects design it could hold some carryover effects
Term
within-subjects design
Definition
participants receive all levels of the IV
Term
between subjects design
Definition
values of the IV are split up between participants
Term
what happens when you calculate pooled variance
Definition
the variance should turn out to be the same for the groups
Term
why is nullifying important
Definition
you need to remove conditions in the independent groups t-test..in the correlated groups t-test it removes individual differences
Term
counterbalancing
Definition
eliminates familiarity or intervening events when using within subjects design
Term
2 uses of correlations
Definition
describe relationships between variables, make inferences about populations
Term
pooled variance
Definition
used for estimating variance after looking at several samples where the mean may vary but the variance is thought to be the same
Term
assumption of the independent groups t-test
Definition
the population variances are homogenous .. also called the homogeneity of variance "o1 2 = o22 = 02"
Term
r2
Definition

explains the proportion of variability in the dependent variable that can be explained by the independent variable

 

aka the coefficient of determination

Term
1 - r2
Definition
the coefficient of alienation
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