The 3-year moving averages for the following data are
| Year | 2019 | 2020 | 2021 | 2022 | 2023 | 2024 |
| Production (in thousand tonnes) | 14 | 20 | 17 | 26 | 29 | 35 |
Answer & explanation
Correct answer: option 4
The correct answer is Option (4) → 17, 21, 24, 30
A 3-year moving average is the mean of each set of three consecutive years, placed against the middle year:
\( \displaystyle 2020: \frac{14 + 20 + 17}{3} = \frac{51}{3} = 17 \)
\( \displaystyle 2021: \frac{20 + 17 + 26}{3} = \frac{63}{3} = 21 \)
\( \displaystyle 2022: \frac{17 + 26 + 29}{3} = \frac{72}{3} = 24 \)
\( \displaystyle 2023: \frac{26 + 29 + 35}{3} = \frac{90}{3} = 30 \)
So the moving averages are 17, 21, 24, 30. There is none for the first year and the last year.