r？ = 0.845 //: The fitting accuracy is average;

When x=7, y=6.5×7+ 17.5=63 //: when the advertising expenditure is 7, the sales volume is 63.

2) If the data 50 and 60 in y are interchanged, the following fitting results are obtained.

Y = 7x+15/:the linear regression equation obtained;

r？ =0.98 //: high fitting accuracy;

When x=7, y=64 //: the advertising cost is 7, the sales amount is 64.

But when x=7, the sales forecast value does not change much!