(c) Calculate the correlation coefficient and state what this indicates about the relation between the two variables. [4]

Question

The following table shows the hours of sunshine, x, during nine days in August and the number of ice creams, y, sold by a beach shop in Cornwall. 

x	4.3	6.9	0.0	10.4	5.2	1.8	8.0	9.2	2.1
y	224	208	123	419	230	184	362	351	196

 (c) Calculate the correlation coefficient and state what this indicates about the relation between the two variables. [4] 

Answer 1

By simply using Excel function CORREL the correlation value between the two arrays is 92.1%, implying a strong positive dependence between the hours of sunshine and number of ice creams sold. Alternatively, this may be calculated using the covariance-correlation formula which states: corr(x,y) =cov(x,y)/(σ_x .σ_y) for σ_x and σ_y the standard deviations of x and y respectively.