5-7 An ACF Example (p234 · Question: Suppose that we had estimated the first 5 autocorrelation coefficients using a series of length 100 observations, and found them to be( from 1 to5):0.207,-0.013,0.086,0.005,-0.022 Test each of the individual coefficient for significance, and use both the box-Pierce and ljung-Box tests to establish whether they are jointly significant · Solution: a coefficient would be significant if it lies outside(0. 196, +0.196) at the 5% level, so only the first autocorrelation coefficient is significant Q5.09andQ*=5.26 Compared with a tabulated x(5=1l.1 at the 5%level, so the 5 coefficients are jointly insignificant5-7 • Question: Suppose that we had estimated the first 5 autocorrelation coefficients using a series of length 100 observations, and found them to be (from 1 to 5): 0.207, -0.013, 0.086, 0.005, -0.022. Test each of the individual coefficient for significance, and use both the Box-Pierce and Ljung-Box tests to establish whether they are jointly significant. • Solution: A coefficient would be significant if it lies outside (-0.196,+0.196) at the 5% level, so only the first autocorrelation coefficient is significant. Q=5.09 and Q*=5.26 Compared with a tabulated  2 (5)=11.1 at the 5% level, so the 5 coefficients are jointly insignificant. An ACF Example (p234)