In the month of January, the number of cases diagnosed of influenza epidemic are given in the following table
| Date | 1 | 2 | 3 | 4 | 5 | 6 | 7 |
| Number of cases | 2 | 0 | 5 | 12 | 20 | 27 | 46 |
The 3-day moving averages are:
Answer & explanation
Correct answer: option 4
The correct answer is Option (4) → \(2.3, 5.6, 12.3, 19.6, 31\)
A 3-day moving average is the mean of three consecutive values; the window then moves one day forward. Seven values give five averages.
\( \displaystyle \frac{2 + 0 + 5}{3} = \frac{7}{3} = 2.33 \)
\( \displaystyle \frac{0 + 5 + 12}{3} = \frac{17}{3} = 5.67 \)
\( \displaystyle \frac{5 + 12 + 20}{3} = \frac{37}{3} = 12.33 \)
\( \displaystyle \frac{12 + 20 + 27}{3} = \frac{59}{3} = 19.67 \)
\( \displaystyle \frac{20 + 27 + 46}{3} = \frac{93}{3} = 31 \)
The options show these values cut off after one decimal place (5.67 is shown as 5.6 and 19.67 as 19.6). Option (4) is the only option that matches all five averages.