EMC Proven Professional – Data Science and Big Data Analytics — Question 20

Before you build an ARMA model, how can you tell if your time series is weakly stationary?

Answer options

• A. There appears to be a constant variance around a constant mean.
• B. The mean of the series is close to 0.
• C. The series is normally distributed.
• D. There appears to be no apparent trend component.

Correct answer: A

Explanation

The correct answer is A because weak stationarity requires both a constant mean and constant variance over time. Option B is incorrect as the mean does not have to be near zero for weak stationarity. Option C is misleading since normality is not a requirement for weak stationarity. Option D does not fully capture the necessity of constant variance in addition to the absence of a trend.