A retailer records its weekly spending on online advertising, x x\,x hundreds of pounds, and the number of online orders, yyy, for a random sample of 24 weeks.
The product moment correlation coefficient between x x\,x and y y\,y is 0.87, and the regression line of y y\,y on x x\,x for these data is
y=118+42.5xy = 118 + 42.5xy=118+42.5x
The advertising spending in the sample ranges from 1.0 to 3.2 hundreds of pounds.
Give an interpretation of the gradient of this regression line.
State, giving a reason, which of the two variables is the explanatory variable.
State, giving a reason, whether the value of the product moment correlation coefficient is consistent with using a linear regression model for these data.
Explain why this model should not be used to estimate the number of online orders in a week when 600 pounds is spent on online advertising.