Psych Exam 4 Class Slide Questions Flashcards
What is a correlation?
Relationship between 2 variables (x and y)
What are the two pieces of information that correlations provide?
Magnitude and direction
What is magnitude?
Degree of relationship between two variables
What is direction?
How the variables are related
What is a positive direction?
As x increases y also increases
What does a negative direction indicate?
As x increases y tends to decrease
What do correlation coefficients assume?
Linear relationships
What is a linear relationship?
Relation represented by a straight line
What do scatterplots graph?
Two variable distribution by placing dots at the value of paired scores
What does the pattern point reveal in a scatterplot?
Direction of the correlation
How is magnitude determined?
How closely data points hug the hug line
What happens with a stronger relationship?
The closer the data points will be to the line
What happens with the variables if there is no correlation?
Value of one variable doesn’t predict value of other variable
What is Pearson’s r?
Single statistic indicating direction and strength of correlation
What does Pearson’s r require?
Multiplying deviations from mean X by mean of Y (cross products)
What is the second step in finding Pearsons r?
Divide by standard deviations and number of pairs
What is the equation for Pearsons r?
r= E (X-X-)(Y-Y-)/ noXoY
What is the value of a perfect positive correlation?
r= +1
What is the value of a perfect negative correlation?
r= -1
What is the value of no correlation?
r= 0
What is a small, moderate, and large correlation strength value?
r=.1 (small), r=.3 (m), r=.5 (l)
What do strong correlations not provide?
Causation
What do non-linear effects do to Pearsons r?
Make it look small
What reduces the effects of Pearsons r?
Restriction of range/talent
What artificially increases the size of Pearsons r?
Discontinuous distributions
What happens to correlations as sample size increases?
They become more accurate
What are correlations determined by?
Specific measures representing the variables/conditions of measurement
What Is the first issue with hypothesis testing?
Nulls are point estimates almost always false
What is the second issue with hypothesis testing?
No “grey area” between significance and non-significance
What does failing to reject the null provide?
Little info for conclusions
What are confidence intervals?
Interval estimates
What do confidence intervals represent?
Range of values where we are likely to find pop value
What is the first reason to use confidence intervals?
Evidence on likely range of possible values of parameters
What do CI’s provide a clear indication of?
How sample size influences accuracy of guessing