4 2. A random sample of 15 days is taken from the large data set for Perth in June and July 1987. The scatter diagram in Figure 1 displays the values of two of the variables for these 15 days. 0 10 15 20 x y 0 Figure 1 (a) Describe the correlation. (1) The variable on the x-axis is Daily Mean Temperature measured in °C. (b) Using your knowledge of the large data set, (i) suggest which variable is on the y-axis, (ii) state the units that are used in the large data set for this variable. (2) Stav believes that there is a correlation between Daily Total Sunshine and Daily Maximum Relative Humidity at Heathrow. He calculates the product moment correlation coefficient between these two variables for a random sample of 30 days and obtains r = −0.377 (c) Carry out a suitable test to investigate Stav’s belief at a 5% level of significance. State clearly ● your hypotheses ● your critical value (3) On a random day at Heathrow the Daily Maximum Relative Humidity was 97% (d) Comment on the number of hours of sunshine you would expect on that day, giving a reason for your answer. (1)