Q.Which of the following can’t be a component of a time series?

The recognised components of a time series are trend, seasonal, cyclical and irregular (random) variation. The mean is a measure of central tendency, not a component, so option (4) is correct.

The fluctuations in a time series are conventionally decomposed into four components:

• Trend (secular trend) — the long-term movement,
• Seasonal variation — regular movements within a year,
• Cyclical variation — wave-like movements over periods longer than a year, …

Cyclical variation has a period longer than a year (typically 2–10 years, like business cycles), so it cannot occur several times in a year; the statement is False. (Movements repeating several times within a year are seasonal, not cyclical.)

Among the components of a time series:

• Seasonal variation is periodic within a year (e.g. monthly or quarterly patterns) — it repeats several times in a year. …