13.49 A financial analyst wants to estimate the monthly expenditure on food (£ 000) by a household based on the size of the household, monthly household income, number of monthly purchases, and number of meals cooked at home per month. He determined the following regression model from a sample of 50 households.

yn = 0.2831 + 0.5729x1t 10.07932

+ 0.0953x2t 10.01832

+ 0.5136x3t 10.04262

+ 0.1538x3t 10.01922 d = 1.04 where yn = monthly grocery expenditure on food x1 = household size x2 = monthly household income x3 = number of monthly purchases x4 = number of meals cooked at home per month The numbers below the coefficients are the coefficient standard errors.

a. Interpret the estimated coefficient on x1.

b. Using the Durbin-Watson statistic, test at the 5%

level the null hypothesis of positive autocorrelation of error terms.

c. Estimate the autocorrelation parameter.