2. CORRELATION Correlation can be easily understood as co relation. Correlation is the average relationship between two or more variables. When the change in one variable makes or causes a change in other variable then there is a correlation between these two variables.
3. Types Of Correlation Positive correlation: r is close to +1. An r value of exactly +1 Negative correlation : r is close to -1. An r value of exactly -1 No correlation: r is close to 0. A correlation greater than 0.8 is generally described as strong , whereas a correlation less than 0.5 is generally described as weak .
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5. Spearman’s Rank C.C. Formula Perfect Negative Correlation No Correlation Perfect Positive Correlation This formula is on the formula sheet so you don’t need to learn it! This formula is on the formula sheet so you don’t need to learn it!
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9. Fertiliser v. Plant Growth Crop A B C D E Fertiliser 12.8 17.1 8.3 6.7 10.2 Yield 103 108 89 75 105
10. First, Rank The Data: Crop A B C D E Fertiliser 12.8 17.1 8.3 6.7 10.2 Fertiliser RANK 2 1 4 5 3 Yield 103 108 89 75 105 Yield RANK 3 1 4 5 2
11. Second, Find The Rank Differences: Crop A B C D E Fertiliser 12.8 17.1 8.3 6.7 10.2 Fertiliser RANK 2 1 4 5 3 Yield 103 108 89 75 105 Yield RANK 3 1 4 5 2 Rank Difference -1 0 0 0 1
12. Third, Square The Rank Differences: Crop A B C D E Fertiliser 12.8 17.1 8.3 6.7 10.2 Fertiliser RANK 2 1 4 5 3 Yield 103 108 89 75 105 Yield RANK 3 1 4 5 2 Rank Difference -1 0 0 0 1 d^2 1 0 0 0 1
13. Now Find “Sigma D Squared” Crop A B C D E Fertiliser 12.8 17.1 8.3 6.7 10.2 Fertiliser RANK 2 1 4 5 3 Yield 103 108 89 75 105 Yield RANK 3 1 4 5 2 Rank Difference -1 0 0 0 1 d^2 1 0 0 0 1
