Examination Assignment 2.2
(Skills: statistical skills, Spearman’s rank correlation, handling statistical data, significance levels, drawing conclusions from results)
1) Complete the Spearman’s rank correlation table (Figure 2.28)
(6 marks)
Figure 2.28 Infant Mortality/Per Capita GDP* (2007)
Country / per capitaGDP (US$) / rank / Infant mortality rate / rank / d / d2
Canada / 38200 / 1 / 4.6 / 11 / -10 / 100
Belarus / 10000 / 6.6
Sweden / 36900 / 2 / 2.8 / 14 / -12 / 144
N. Zealand / 27300 / 6 / 5.7 / 9 / -3 / 9
France / 33800 / 4 / 3.4 / 13 / -9 / 81
U.K. / 35300 / 3 / 5.0 / 10 / -7 / 49
India / 27000 / 7 / 34.6 / 1 / 6 / 36
Spain / 33700 / 5 / 4.3 / 12 / -7 / 49
Poland - 32 -McCabe Page 32 10/11/2015Poland / 16200 / 8 / 7.1 / 7 / 1 / 1
Philippines / 3300 / 22.1
Egypt / 5400 / 29.5
Romania / 10000 / 24.6
Brazil / 9700 / 27.6
Russia / 14600 / 11.1
/ =
*per capita GDP (or Gross Domestic Product) means the average income per person
2) Use the following formula to calculate the Spearman’s rank correlation coefficient (rs) between per capita GDP and infant mortality.
Spearman’s rank
(2 marks)
3) State the Null Hypothesis (H0)
(1 marks)
4) Using the correlation graph (Figure 2.28) give the level of significance of your results. Can you accept or reject the Null Hypothesis (H0)
(3 marks)
5) What conclusions can be drawn from your results and what are the reasons for them?
(7 marks)
Exam hint:
Remember that correlation can be either positive or negative. Both are equally valid as long as the trend is obvious or the coefficient is significant. The coefficient can only vary between +1 and –1 (if your coefficient is larger that this then go back and check your calculations!).
6) Assess the strengths and weaknesses of the Spearman’s rank correlation test for analysing data.
(6 marks)
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