Use Annual Income independent variable and Mortgage Amount as dependent variable, to find a simple linear regression.

(You can use either regression from Data Analysis tool or using Trendline through scatter plot)

Use the coefficient values to calculate the estimated Mortgage Amount in sheet2.

Then calculate the forecast error and square error for each record.

At last, calculate the average error and and RMSE (Root Mean Squared Error).

What are average error [ Select ] ["52536.42577", "27600.5931", "-0.2"] and RMSE [ Select ] ["27600.5931", "-0.2", "52536.42577"] ?