Key Terms associated with Correlation Either write a definition or draw a diagram to illustrate the terms below (see page 28 & 29). –Correlation –Scatter graphs –Independent variable –Line of best fit –Dependent variable –Residual value –Positive linear relationship –Negative linear relationship Spearman’s Rank Correlation Coefficient -A statistical measure which shows the strength of a relationship between two variables. -It also outlines the type of relationship whether positive or negative. -Minimum of 10 sets of paired values needed for this test to be statistically reliable. -A strong correlation indicates that there is a link between the two factors but not that one causes the other. -For example there may be a strong correlation between the incidence of sunburn and the sale of ice cream, but this does not imply that ice cream causes sunburn. -This test simply indicates that there may be a causative link which can be explored with further investigation.
Spearman’s Rank Write out the formula for the calculation of r s Interpretation of r s Increasing Significance Perfect No Perfect Negative Correlation Positive Linear Relationship How do we know if an answer is close enough to 1 to be considered significant?
Questions - Page Explain why 95% is a cut off point for significance. How do you calculate degrees of freedom? What do significance levels of 95%, 99% and 99.9% mean? Carefully study the worked example on page 30 & 31.