Irregular variations in a time series are caused by:
(A) Floods
(B) Natural calamities
(C) Labour strike
(D) Climate changes
Choose the correct answer from the options given below:
Answer & explanation
Correct answer: option 3
The correct answer is Option (3) → (A), (B), and (C) only
Irregular (random) variations are caused by sudden, unpredictable events that follow no pattern and cannot be forecast, such as floods, earthquakes, wars, epidemics and strikes. Changes that repeat within a year give seasonal variations, and long-run changes give the trend.
So a cause is irregular only if it is a one-off shock, not a regular or long-run change.
Checking the statements
(A) Floods — Correct. A flood is a sudden, unforeseen event.
(B) Natural calamities — Correct. Earthquakes, cyclones and similar calamities occur without any regular pattern.
(C) Labour strike — Correct. A strike is an unexpected disruption that cannot be predicted from past data.
(D) Climate changes — Incorrect. Climate changes over the seasons repeat every year (seasonal variation), and long-term climate change shows in the trend.
CBSE Applied Mathematics (Class XII):
Index Numbers and Time-based Data
