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WARNING: a STRONG positive correlation doesn't necessarily mean that one factor CAUSES the
other.
NOTE:
When asked in an exam question to explain why the student is wrong if he/she suggests a
positive/ negative correlation then state:
1. Correlation does not imply causation
2. There must be a third causal factor
3. Include an example of a possible third factor
x is the independent variable and y is the dependent since the values of x are not subject to
random variation and are chosen.…read more

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However, if one or both of your variables is skewed (i.e. asymmetrical) or bimodal (i.e. data
points occur in 2 groups) then this test could give a false result.
WHEN CONDUCTING A PMCC TEST:
1. State the null hypothesis and alternative hypothesis for the test:
Onetailed test H0: = 0 H1: > 0 or H1: < 0
Two tailed test H0: = 0 H1: 0
2. State what represents:
where represents the population correlation coefficient
3.…read more

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USING THE FORMULA:
Example: At a dog show, two judges ranked 8 of the Labradors (AH) in the following order.
Calculate the rs and comment on your result.…read more

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If x falls within the range if data, then the yvalue is reliable. This is called INTERPOLATION.
If x falls outside the range of data, then the estimated yvalue is unreliable. This is called
EXTRAPOLATION.
WHY IS PMCC A BETTER TEST THAN SPEARMANS RANK?
PMCC is better since it takes the actual values into account and not just the ranks.
Thus, it has more information than Spearman's and will therefore provide a more discriminatory
test.…read more

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