Nov 2018 Q1
a) Explain the term Coefficient of Correlation in forecasting. (3 marks)
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A coefficient of correlation is a statistical measure of the degree to which changes to the value of one variable predict change to the value of another. In positively correlated variables, the value increases or decreases in tandem. In negatively correlated variables, the value of one increases as the value of the other decreases.
b) The study time in minutes and the number of errors on a mock examination paper made by ten (10) ICAG students are given below:
Required:
i) Determine how many errors a student would make in the examination if he studied for 280 minutes. (8 marks)
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i.e. a student who studied for 280 minutes is expected to make 11 errors.
ii) Determine the expected change in number of errors if there is 1 minute change in study time. (2 marks)
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Expected change in number of errors if there is 1 minute change in study time is 0.064 minutes or 3.84 seconds.
iii) Compute Pearson Product Moment Correlation coefficient between study time and number of errors made. (5 marks)
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iv) Compute the coefficient of determination between study time and number of errors made and comment on your results. (2 marks)
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The coefficient of determination between study time and number of errors made is 85.77%
This means 85.77% of the variation in number of errors made is due to study time.