Lecture 8 Flashcards
Which variable goes on which axis?
IV on X axis
DV on Y axis
What do correlations look for?
- If two variables co-vary/ co-relate? Or does y vary as a function of X? If so what strength is the relationshiP?
- Do they move in same direction? or opposite directions?
How do you make a scatter plot in SPSS?
Graphs - legacy dialogs - scatter/ dot - select simple scatter - enter variables - ok
Define co-variance
The degree to which 2 variables vary together (in same/ opposite way). Basically the level/ strength of the relationship
What is mean by ‘scaling the co-variance?’
Standardising the covariance so it is between -1 and +1
What does the distance ‘r’ must be from 0 to be a significant correlation depend on? (calculated by SPSS)
Sample size
What does scaling the covariance give you?
Correlation coefficient, Pearson’s R. Pearsons product moment correlation coefficient ‘p’
What were Cohen (1988)’s boundaries for correlation strengths?
Small: 0.1 - 0.29
Medium: 0.3 - 0.49
Large: 0.5 - 1
How do you work out the significance of a correlation on SPSS?
Analyse - correlate - bivariate - add variables - select pearson - must be less then 0.05 to be significant
What is the regression line?
It’s a straight line - average plot direction.
What does the regression line allow us to predict?
Enables us to predict y from X
What is the regression equation?
Predicted value of Y = bX+a
B = steepness of regression line
A = y-intercept, value of y when x=0
What would r = 0 mean?
There is no evidence of a linear relationship between x and Y? Doesnt mean there is no relationship!
Even if there is a correlation? What doesnt it tell us?
Which variable causes the other? Or if an EV causes the relationship
How do you calculate the regression line in SPSS?
Double click scatterplot - chart editor opens - used ‘Add fit at total button’ - select linear
