The 5-year moving averages for the following data are
| Year | 2017 | 2018 | 2019 | 2020 | 2021 | 2022 | 2023 | 2024 |
| Production (in thousand tonnes) | 30 | 34 | 31 | 38 | 42 | 40 | 44 | 46 |
Answer & explanation
Correct answer: option 2
The correct answer is Option (2) → 35, 37, 39, 42
A 5-year moving average is the mean of five consecutive values, placed against the middle (third) year of the five:
\( \displaystyle 2019: \frac{30 + 34 + 31 + 38 + 42}{5} = \frac{175}{5} = 35 \)
\( \displaystyle 2020: \frac{34 + 31 + 38 + 42 + 40}{5} = \frac{185}{5} = 37 \)
\( \displaystyle 2021: \frac{31 + 38 + 42 + 40 + 44}{5} = \frac{195}{5} = 39 \)
\( \displaystyle 2022: \frac{38 + 42 + 40 + 44 + 46}{5} = \frac{210}{5} = 42 \)
So the 5-year moving averages are 35, 37, 39, 42. There are none for the first two and the last two years.