Suppose Zt = 2 + Xt -2Xt-1+Xt-2, where {Xt} is zero-mean stationary series with autocovariance function.
Calculate the autocovariance of Zt
Suppose Zt = 2 + Xt -2Xt-1+Xt-2, where {Xt} is zero-mean stationary series with autocovariance function....
Yt = 5 − 2t + Xt, where {Xt} is stationary with mean 0 and autocovariance function γk. Now, let Wt = Yt − Yt−1. (a) Find the mean function for {Wt}. (b) Find the autocovariance function for {Wt}. (c) Is {Wt} stationary? Why or why not?
Exercise 2.31 Superposition [] Given two independent weakly stationary time series Xt and Yi) with autocovariance functions x(h) and y (h), show that Zt- Xt +Yt is also weakly stationary, with autocovariance function given by yz(h)-x(h)y(h).
1. Let {Xt} be a stationary process with mean μt = E(Xt) = 0 and autocovariance function γX(k) = E(XtXt−k) - μ2 = E(XtXt+k) - μ2. De ne Yt = 5 + 2t + Xt. (a) Find E(Yt), the mean function for Yt. (b) Find γY (k), the autocovariance function for Yt in terms of γX (k). (c) Is Yt stationary? Explain. (d) De ne a new process Wt as Wt = Yt − Yt−1. Find E(Wt) and γW (k)....
2. Suppose that Ya ut where the ut are iid Normal with mean zero and variance σ2, but that you mistakenly think Yt is difference stationary. You therefore construct a new series a) Are the Xt i.i.d.? Explain b) Is X stationary? Explain c) Calculate the mean, variance, and autocorrelation function of X d) How does the answer you obtained in (c) compare with the mean, variance and autocor- relation function of Y? 2. Suppose that Ya ut where the...
I. (5 points) Let {X, } be a stationary series with mean μ and autocovariance function 7(), and icz Show Y is also stationary for a, ER, iE Z 2. (5 points) Let {Xi be the process Xi A cos(wt) Bsin(t),t 1,2, ., COS
Problem 3 Consider a random walk on the integers. Suppose we start from 0, and at each step, we either go left or right with probability 1/2, ie, Xo--0, and Xt+1 Xt+Zt, where Zt-1 with probability 1/2, and Zt1 with probability 1/2. What is the probability distribution of XT? What is E(X) and Var(XT)? Problem 3 Consider a random walk on the integers. Suppose we start from 0, and at each step, we either go left or right with probability...
Let Yt = β0 + β1t + Xt with {Xt} zero mean stationary with acf γk and β’s constant. Is {Yt} stationary? Is ∇Yt?
2. Let (et) be a zero mean white noise process with variance 1. Suppose that the observed process is h ft + Xt where β is an unknown constant, and Xt-et- Explain why {X.) is stationary. Find its mean function μχ and autocorrelation function p for lk0,1,.. a. b. Show that {Yt3 is not stationary. C. Explain why w. = ▽h = h-K-1 is stationary. d. Calculate Var(Yt) Vt and Var(W) Vt . (Recall: Var(X+c)-Var(X) when c is a constant.)...
Let { be a zero-mean stationary process and let a and b be constants. (a) (5 points) If Xi a+bt+St+Yi, where St is a seasonal component with period 12, show that ▽12V is stationary and express its autocovariance function in terms of that of { (b) (5 points) If X1-(a + bt)Sİ + Y. where Sı is a seasonal component with period 12, show that Vi2 is stationary and express its autocovariance function in terms of that of {
Problem 2.1 Consider a process consisting of a linear trend with an additive noise term consisting of independent random variables Zt with zero means and variances σ2, that is, where Arßi are fixed constants. a) Prove that Xe is non-stationary b) Prove that the first difference series VX,-X, -X-1 is stationary by finding its mean and autocovariance function. c) Repeat part (b) if Z is replaced by a general stationary process, say Y,, with mean function py and autocovariance function...