Time Series: Seasonal Indices (Grade 12)
Free printable Grade 12 General Mathematics worksheet: calculate seasonal indices by the average percentage method and deseasonalise data (ACMGM090).
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Grade 12 · Math worksheet
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Time Series: Seasonal Indices (Year 11-12 General Mathematics)
Quarterly heater sales (units) recorded over 3 years by quarter. Use the average percentage method to find the seasonal indices, interpret them, and deseasonalise a value. All indices are computed from the table.
| Q1 | Q2 | Q3 | Q4 | |
|---|---|---|---|---|
| Year 1 | 34 | 56 | 87 | 72 |
| Year 2 | 39 | 59 | 99 | 76 |
| Year 3 | 43 | 64 | 103 | 82 |
- 1.Using the average percentage method, calculate the seasonal index for Q1 from the table (round to 1 decimal place). The seasonal indices are then scaled so they average 100.
- 2.Using the average percentage method, calculate the seasonal index for Q2 from the table (round to 1 decimal place). The seasonal indices are then scaled so they average 100.
- 3.Using the average percentage method, calculate the seasonal index for Q3 from the table (round to 1 decimal place). The seasonal indices are then scaled so they average 100.
- 4.Using the average percentage method, calculate the seasonal index for Q4 from the table (round to 1 decimal place). The seasonal indices are then scaled so they average 100.
- 5.The seasonal index for Q3 is 142. Interpret what this tells you about Q3 compared with an average quarter.
- 6.The actual Q3 figure in Year 1 was 87 units. Using the Q3 seasonal index of 142, calculate the deseasonalised figure (to 1 decimal place). Deseasonalised value = actual value divided by (index / 100).
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