Considera sample of 50 observations from a stationary process with

Lag | ACF | PACF ------------------------- 1 | 0.9 | 0.9 2 | 0.85 | 0.4 3 | 0.7 | 0.1

How do I suggest an appropriate model using the above information.

From my understanding, significance of ACF and PACF values were checked using:$ H_{0}: \rho=0$ rejected at 5% level of significance if $|\rho| >\frac{1.96}{\sqrt(50)}$. I found that only the last value of pacf is non significant.

(1)Can I say that the model is ARMA(2,3)? (2) how to decide if it is AR, MA or ARMA?

NB: this was a question asked in an examination. To be worked out manually.

Considera sample of 50 observations from a stationary process with

$$\begin{array}{c|c|c|} \text{lag} & \text{acf} & \text{pacf} \\ \hline 1 & 0.9 & 0.9 \\ \hline 2& 0.85 & 0.4\\ \hline 3&0.7&0.1\\ \hline \end{array}$$

How do I suggest an appropriate model using the above information.

From my understanding, significance of ACF and PACF values were checked using:$ H_{0}: \rho=0$ rejected at 5% level of significance if $|\rho| >\frac{1.96}{\sqrt(50)}$. I found that only the last value of pacf is non significant.

(1)Can I say that the model is ARMA(2,3)? (2) how to decide if it is AR, MA or ARMA?

NB: this was a question asked in an examination. To be worked out manually.