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# Spearman Rank

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IB Geography, Population & statistics

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### Spearman Rank

1. 1. Spearman’s Rank <br />Statistical Analysis to show Relationship Strength.<br />www.i-study.co.uk<br />
2. 2. Is birth rate connected to economic development in Central and South American countries?<br />Data taken from Philip’s International School Atlas (2nd Edition) published 2006 <br />www.i-study.co.uk<br />
3. 3. SPEARMAN’S RANK CORRELATION COEFFICIENT<br />It says …<br />It allows us to …<br />Compare the <br />RANK ORDER <br />of TWO Data Sets<br />www.i-study.co.uk<br />
4. 4. The total of<br />6 x<br />Spearman’s Rank Correlation Coefficient<br />The DIFFERENCES between the RANKS assigned to each ‘price’ SQUARED<br />The number of different factors in the study<br />www.i-study.co.uk<br />
5. 5. The Maths<br />For Argentina:<br />d (rank difference) = 8.5<br />So d2 = 72.25<br />Repeat this calculation for each country<br />Multiply the sum of all the d2 values by 6 to give the top line of the equation<br />n = the number of countries in the sample =12. <br />n³ - n : 1728 – 12 = 1716 (now we have the bottom line of the equation)<br />Plug in the appropriate numbers to the full equation:<br /> your answer for step 4 <br /> your answer for step 6<br />R = 1-<br />www.i-study.co.uk<br />
6. 6. What does this R value mean?<br />The closer Ris to +1 or -1, the stronger the likely correlation. <br />Perfect positive correlation is +1 <br />Perfect negative correlation is -1. <br />Therefore, what sort of relationship do your calculations suggest?<br />www.i-study.co.uk<br />
7. 7. What is it showing?<br />Total Disagreement<br />Overall Neither <br />Agree or Disagree<br />Total Agreement<br />rs close to -1<br />rs close to 1<br />rs close to 0<br />www.i-study.co.uk<br />
8. 8. The significance of the relationship!<br /><ul><li>The R value must be looked up on the Spearman Rank significance table.
9. 9. 'degrees of freedom' : This is the number of pairs in your sample minus 2 (In this case, 12 – 2 = 10)
10. 10. Using the R value (y axis) the degrees of freedom value (x axis) plot the position of the graph (next page).</li></ul>www.i-study.co.uk<br />
11. 11. www.i-study.co.uk<br />
12. 12. Tasks<br />Repeat this exercise for the same countries, but this time replace the birth rate data with the data for life expectancy.<br />www.i-study.co.uk<br />