Question

What factors affect the strength (or size) of a correlation between two variables

Answer 1

Factors affecting the magnitude or size of correlation:

• Is the relation linear?

r can only be large if the association between the X and Y variables is linear. (in case of only linear association)

• Are the distribution shapes of scores on X and Y the same?

r of +1 tells us that there is a one to one mapping of locations (in z score terms) of X and Y values. It is not possible to get a one to one mapping for all scores if the distribution shapes for X and Y are different from each other ( assume that both X and Y are normally distributed)

• 3. Are there bivariate outliers in the X, Y scatter plot?

similarly other factors are as follows

• how reliable are X ,Y measure?
• is there restricted range for scores on X and/or Y?
• Does the samples include groups of people for whom X,Y association differs?
• sampling error

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