Calculate three yearly moving averages for the following data
| Year | 2016 | 2017 | 2018 | 2019 | 2020 | 2021 |
| Production (thousand tonnes) | 200 | 220 | 231 | 254 | 202 | 243 |
Answer & explanation
Correct answer: option 2
The correct answer is Option (2) → 217, 235, 229, 233
A three-yearly moving average is the mean of each set of three consecutive years, placed against the middle year:
\( \displaystyle 2017: \frac{200 + 220 + 231}{3} = \frac{651}{3} = 217 \)
\( \displaystyle 2018: \frac{220 + 231 + 254}{3} = \frac{705}{3} = 235 \)
\( \displaystyle 2019: \frac{231 + 254 + 202}{3} = \frac{687}{3} = 229 \)
\( \displaystyle 2020: \frac{254 + 202 + 243}{3} = \frac{699}{3} = 233 \)
So the moving averages are 217, 235, 229, 233.