A management accountant is analyzing data relating to retail sales on behalf of marketing colleagues. The marketing staff believe that the most important influence upon sales is local advertising undertaken by the retail store. The company also advertises by using regional television areas. The company owns more than 100 retail outlets, and the data below relate to a sample of 10 representative outlets.

The data have been partly analyzed and the intermediate results are available below.

You are required to examine closely, using coefficients of determination, the assertion that the level of sales varies more with movements in the level of local advertising than with changes in the level of regional company advertising. (8 marks)
That the co-efficient of determination for y and x1 may be calculated from

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Local advertising by the retailthe company store (£000 Regional advertising by Monthly sales (E000 per month) Outlet number (E000per month) X2 4 220 230 240 340 420 460 520 600 720 800 2 12 12 2 10 16 18 20 26 30 36 46 4 5 16 15 14 20 10 уг-2451 300 ΣΧ1у- 58040 1533 Σχ2У -121100 D2= 212D 2780 =4550 y 2 ΣΧ1- 113 ΣΟ- 22 = 6120 ΣΧ1X2=