1. Correlation Population data: Lesson 5

2. Finding relationships  Two sets of data may well be ‘correlated’, that is, there is some sort of statistical relationship between them.  This is not to say that the values of one data set are causing the values of the other, but a data value from one set can be used to predict a corresponding value in the other.  We plot scatter diagrams with lines of best fit to achieve this. 2

3. Finding relationships Overall, there appears to be no relationship between birth rates and death rates, except in Africa where there appears to be a positive correlation. 3

4. Finding relationships Comparing birth rates to infant mortality rates, however, shows a ‘strong’ positive correlation. This makes logical sense, given that parents are likely to want larger families if many children die young. Note: Line of best fit doesn’t necessarily go through the origin 4

5. Finding relationships The correlation between death rate and life expectancy overall has a weak negative correlation, although Africa on its own demonstrates a strong correlation. Oceania seems to have no correlation. 5

6. Using relationships Niger has a death rate of 11 deaths per 1000 people. Niger has a life expectancy of 58. Algeria has a life expectancy of 71. Algeria has a death rate of 6. Estimate Niger to have a life expectancy of 57. Estimate Algeria to have a death rate of 5. 6

7. Ignoring the trend Sometime times pieces of data don’t follow the trend of the other pieces of data. These can be considered as outliers. There may well be a reason for this exception to ignore the trend (Mayotte is a very small island). Mayotte has a death rate of 31 and a infant mortality of 4. 7

8. Finding relationships  Plot scatter graphs with birth or death rates on one axis and another data set on the other.  A good selection of other data is available on the World Population Data Sheet. There is lots more on the internet!  Comment on the correlation in your graphs and whether there is a reason for this. 8

9. Core Maths Support Programme 60 Queens Road Reading RG1 4BS E-mail cmsp@cfbt.com Call 0118 902 1243