Question 4 (b)
Identifying the component of a time series in five situations
5 marks
- Time to write
- About 10 minutes
Question
Question 4 (b) · 5 marksWhich component of a time series would you mainly associate with each of the following?
A lockout in a factory that delays production for 20 days
Sales of a textile firm at the time of Eid
A fall in the death rate owing to progress in science
A period of prosperity
The need for greater wheat production owing to a steady increase in population
Reworded from the university paper; the task is the same. The original paper belongs to the University of Delhi. See DU's question bank.
Before you write
Read off the question and its marks
Read from the question
- (i)–(v)5 items, each marked on its own: give each its share.
Write it in this order
The parts stand alone: start with the one you are surest of.
- Read; underline the asks; jot your points 1 min
- 1 (i) with reason 1 mark 2 min
- 2 (ii) with reason 1 mark 2 min
- 3 (iii) with reason 1 mark 2 min
- 4 (iv) with reason 1 mark 1 min
- 5 (v) with reason 1 mark 1 min
- Check: every ask answered, key terms underlined 1 min
Short on time? A few lines on every part beat a full answer to one: each part is capped at its own marks.
Try it first. About 10 minutes for 5 marks. Write it out, then open the solution.
Solution
Hover or tap a marked figure, like 72,000, to see how it is made and where else it appears.
The four components. A time series is analysed into components, combined by an additive or a multiplicative model:
- Secular trend (T): the smooth long-run growth or decline over many years.
- Seasonal variation (S): regular ups and downs that recur within a year, linked to seasons, festivals and customs.
- Cyclical variation (C): the alternation of prosperity, recession, depression and recovery, each cycle taking more than a year.
- Irregular variation (I): erratic, unforeseen, short-term movements from chance events such as strikes, lockouts, floods or fires.
(i) A lockout that holds up production for 20 days: irregular variation. It is a sudden, one-off event that cannot be foreseen from the pattern of the series and lasts only a short time.
(ii) Sales of a textile firm at the time of Eid: seasonal variation. Demand for clothes rises around the same festival every year, a regular pattern within the year.
(iii) A fall in the death rate because of progress in science: secular trend. Medical progress lowers the death rate gradually and steadily over a long period.
(iv) A period of prosperity: cyclical variation. Prosperity (boom) is one phase of the business cycle, lasting some years before giving way to recession.
(v) The need for more wheat production because of a steady rise in population: secular trend. Population, and with it the demand for food, rises slowly and persistently over the long run.
| Situation | Component |
|---|---|
| (i) Lockout for 20 days | Irregular |
| (ii) Sales at Eid | Seasonal |
| (iii) Falling death rate | Secular trend |
| (iv) Period of prosperity | Cyclical |
| (v) Wheat for a growing population | Secular trend |
Where the 5 marks sit
| # | Component | Marks |
|---|---|---|
| 1 | (i) with reason | 1 |
| 2 | (ii) with reason | 1 |
| 3 | (iii) with reason | 1 |
| 4 | (iv) with reason | 1 |
| 5 | (v) with reason | 1 |
| Total | 5 |
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