1. Spearman’s Rank Statistical Analysis to show Relationship Strength. www.i-study.co.uk

2. Is birth rate connected to economic development in Central and South American countries? Birth rateRankGNP per capita ($US) Rankdd2d2 Argentina1712 460 Belize296510 Bolivia242590 Brazil178020 Chile1610 500 Colombia216820 Costa Rica199530 El Salvador274980 Nicaragua253300 Panama206870 Peru215370 Uruguay149070 Data taken from Philip’s International School Atlas (2nd Edition) published 2006 www.i-study.co.uk

3. SPEARMAN’S RANK CORRELATION COEFFICIENT It says … It allows us to … Compare the RANK ORDER of TWO Data Sets Compare the RANK ORDER of TWO Data Sets www.i-study.co.uk

4. Spearman’s Rank Correlation Coefficient The total of 6 x The DIFFERENCES between the RANKS assigned to each ‘price’ SQUARED The number of different factors in the study www.i-study.co.uk

5. The Maths For Argentina: 1.d (rank difference) = 8.5 2.So d 2 = 72.25 3.Repeat this calculation for each country 4.Multiply the sum of all the d 2 values by 6 to give the top line of the equation 5.n = the number of countries in the sample = 12. 6.n³ - n : 1728 – 12 = 1716 (now we have the bottom line of the equation) 7.Plug in the appropriate numbers to the full equation: your answer for step 4 your answer for step 6 R = 1- www.i-study.co.uk

6. What does this R value mean? The closer R is to +1 or -1, the stronger the likely correlation. Perfect positive correlation is +1 Perfect negative correlation is -1. Therefore, what sort of relationship do your calculations suggest? www.i-study.co.uk

7. What is it showing? Total Disagreement Total Agreement Overall Neither Agree or Disagree r s close to 1r s close to 0 r s close to -1 www.i-study.co.uk

8. The significance of the relationship! The R value must be looked up on the Spearman Rank significance table. 'degrees of freedom' : This is the number of pairs in your sample minus 2 (In this case, 12 – 2 = 10) Using the R value (y axis) the degrees of freedom value (x axis) plot the position of the graph (next page). www.i-study.co.uk

10. Tasks Repeat this exercise for the same countries, but this time replace the birth rate data with the data for life expectancy. www.i-study.co.uk