Time Series Analysis ARIMA Models 1 — Questions and Answers
Question 1: What does the 'I' in ARIMA stand for?
- Integrated (Correct answer)
- Inverse
- Iterative
- Indexed
Correct answer: Integrated
The 'I' in ARIMA stands for Integrated, referring to the differencing applied to make the series stationary.
Question 2: In an ARIMA(p,d,q) model, what does the parameter 'p' represent?
- Order of the autoregressive component (Correct answer)
- Number of differences
- Order of the moving average component
- Seasonal period
Correct answer: Order of the autoregressive component
The parameter 'p' specifies the order of the autoregressive (AR) component, indicating how many lagged values are used.
Question 3: Which plot is most commonly used to determine the MA order 'q' in an ARIMA model?
- Autocorrelation Function (ACF) (Correct answer)
- Partial Autocorrelation Function (PACF)
- Residual plot
- Spectral density plot
Correct answer: Autocorrelation Function (ACF)
The ACF plot shows a sharp cutoff after lag q for a pure MA process, helping identify the MA order.
Question 4: What does the PACF plot help identify in an ARIMA model?
- The AR order 'p' (Correct answer)
- The MA order 'q'
- The differencing order 'd'
- The seasonal period
Correct answer: The AR order 'p'
The PACF cuts off sharply after lag p for a pure AR process, making it useful for selecting the AR order.
Question 5: What is the purpose of differencing in an ARIMA model?
- To achieve stationarity (Correct answer)
- To remove seasonality only
- To increase autocorrelation
- To normalize residuals
Correct answer: To achieve stationarity
Differencing removes trends and unit roots, transforming a non-stationary series into a stationary one.
Question 6: An ARIMA(0,1,0) model is equivalent to which simple forecasting method?
- Random walk (Correct answer)
- Simple moving average
- Linear regression
- Exponential smoothing
Correct answer: Random walk
ARIMA(0,1,0) applies one difference with no AR or MA terms, which is the definition of a random walk model.
Time Series Analysis ARIMA Models 1
What does the 'I' in ARIMA stand for?