Problem 2
a) If we increase TV ads expenditures in March 2011 by 2500 PLN, we expect that sales increase by 42,23 * 2500=105575 PLN in April 2011, ceteris paribus.
b) Estimated variance of error term will be RSS/(n-K)= 0,5218/(20-4)=0,3216
c) t0,05=2,11991
Pb3-tα*Sb3<β3<b3+tα*Sb3=1-α
-0,6222-2,11991*2,475<β3<-0,6222+2,11991*2,475
-5,86898<β3<4,624577Confidence interval is equal to:(-5,86898; 4,624577)
d) BIC=lnei2n+K*ln(n)n, BIC1 –model in the introduction, BIC2 – model in sub pointBIC1 = ln(0,521820) + 4*ln(20)20=-3.047
e) BIC2 = ln(3,23821) + 2*ln(21)21= -1.580BIC1<BIC2Better is model in introduction (BIC1).
Lajira