Question 5 (a) A study was made by a retail merchant to determine the relation between weekly advertising expenditure (x, in S'000) and sales (y, in $'000). Twelve weeks are selected randomly and the summaries of observed data are given below: [x =41, [y=544.5, _x' = 156.5, _ y' =25129.25, ) xy = 1913.25 Find the "best fit' equation. [4 marks] Calculate the sample correlation coefficient and interpret the result. [4 marks] (b) A chain store uses two forms of advertising to promote sales of certain lines of food products every week. The first form of promotion is through advertising in the daily newspaper(s) and the second form is through the distribution of the discount coupons to residential buildings before the week of the promotion. In order to study the effects of these 2 types of promotional expenditures, 12 stores are selected at random where a certain product line was recently promoted using both forms of promotions. The following outputs are extracted from the computer software in modelling the sales of that product line on the 2 types of promotional expenditures. Coefficient Standard error Intercept 5.5957 Advertising 15.5804 1.3399 Coupon 4.1866 0.9450