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Please question in the image below. Below that, there are two more images with the equations that are referenced. PLEASE help!! THankyou!!!!! First, consider one-step-ahead

Please question in the image below. Below that, there are two more images with the equations that are referenced. PLEASE help!! THankyou!!!!!

image text in transcribedimage text in transcribedimage text in transcribed
First, consider one-step-ahead prediction. That is, given {x1, . .., Xn), we wish to forecast the value of the time series at the next time point, Xn+1. The BLP of Xn+1 is of the form *n+1 = OnlXn + Pn2Xn-1+ . . . + pan*1, (3.61) where we now display the dependence of the coefficients on n; in this case, ax in (3.59) is on,n+1-k in (3.61), for k = 1, ..., n. Using Property 3.3, the coefficients {on1, pn2, . . ., dnn } satisfy E| ( In+ 1 - _ Dnj *n+1-j ) In+1-k = 0, k = 1,..., n, j=1 or n onjy ( k - j) = y(k), k = 1,...,n. (3.62) 1=1 The prediction equations (3.62) can be written in matrix notation as Inon = Vn, (3.63) where I'm = {y(k - j) )" is an nxn matrix, on = (Pal, . . ., Inn)' is an n x 1 vector, and yn = (y(1). . . ., y(n))' is an n X 1 vector.Part 1, PACF Suppose a process {x } is stationary with zero mean and ACF p(.). Let Rn = [p(i - ))],j=1. In addition, let Ph = (p(1), ..., p(h) ) and let pn = (p(h), ..., p(1) ) be the reversed vector. (A) Let x7+ 1 denote the BLP of *n+ 1 given Xn, ."., X1 [see (3.61)]: Xh+1 = a1Xnt ... + anx1. Prove p(h) - Ph-1R7-1Pn-1 an 1 - Ph-1RR-1Pn-1 (Note that, this result proves Property 3.4.) Hint: Write the prediction equations (3.63) as RnAn = Pn, where An = (a1, ..., an)'. Moreover, write RnAn = Pn in the partitioned form as Rn-1 Pn-1 'Ph-1 Ph-1 1 ( An-1 ) = (p(h)) an where An is partitioned as An = (An-1, ann)'.Property 3.4 The Durbin-Levinson Algorithm Equations (3.64) and (3.66) can be solved iteratively as follows: doo = 0. P. = y(0). (3.68) For n 2 1, 106 3 ARIMA Models p(n) - In- Pan = 2k=1 0n-1.k p(n - k) 1 - EX-1 K= 1 0n-1.K P (k) " (1 - dan); (3.69) where, for n 2 2, Pak = $n-1.k - Dan0n-In-ks k = 1,2. ...,n- 1. (3.70) The proof of Property 3.4 is left as an exercise; see Problem 3.13

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