1. Correlation 1 Scatter diagrams Measurement of correlation Using a calculator Using the formula Practice qs

2. Scatter diagrams Scatter diagrams illustrate bivariate data that is when two variables are compared. Draw scatter diagrams to illustrate positive correlation, negative correlation and no correlation. How well the variables fit to a straight line of best fit is the measure of correlation they exhibit. The two types of correlation are positive and negative.

3. Product Moment Correlation Coefficient (PMCC) The product moment correlation coefficient r is a statistical measure of how well each data point lies on a straight line It has a value between 1 (perfect positive correlation) and -1 (perfect negative correlation). In the exam questions if the original data is given then it is acceptable to use a calculator to calculate r. Some times summary statistics are given instead of the original data then the formula for r given in the formula book is used.

4. Jan 07 q3

6. Using a calculator to calculate PMCC x135 y3711 Stats mode Enter the data as two lists GRPH F1 (should draw a scatter graph for the data) CALC (note F1 leads to the statistics for each data set separately) F2 which looks like a X, then F2 ( a + bx) This should give the results a = 1, b = 2 and r = 1 the other results can be ignored

7. June 06 q1 (example of using a calculator calculate PMCC

10. One for you to try (June 07 q1)

11. Product Moment Correlation Coefficient The product moment correlation coefficient, r, has a value between 1 (perfect positive correlation) and -1 (perfect negative correlation). It can be calculated from summary statistics as follows:

12. Jan 08 (q2 using the formula)