x y x^2 xy
1 1 1 1
2 1 4 2
3 2 9 6
4 2 16 8
5 4 25 20
Sum 15 10 55 37
(i)
"b=\\frac{n\\sum_{i=1}^nx_iy_i-\\sum_{i=1}^nx_i\\sum_{i=1}^ny_i}{n\\sum_{i=1}^nx_i^2-(\\sum_{i=1}^nx_i)^2}=\\frac{5*37-15*10}{5*55-15^2}=0.7"
"a=\\frac{\\sum_{i=1}^ny_i-b\\sum_{i=1}^nx_i}{n}=\\frac{10-0.7*15}{5}=-0.1"
The least square line: "y=a+bx=-0.1+0.7x"
(ii)
When Advertising increases by $100, the Sales increases by $700.
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