3 Jane wonders whether the number of wasps entering a wasp's nest per 5 second interval can be modelled by a Poisson distribution with mean \(\mu\). She counts the number of wasps entering the nest over 60 randomly selected 5 -second intervals. The results are shown in Fig. 3.1.
\begin{table}[h]
| Number of wasps | 0 | 1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 | 9 | \(\geqslant 10\) |
| Frequency | 0 | 2 | 5 | 5 | 12 | 10 | 10 | 11 | 1 | 4 | 0 |
\captionsetup{labelformat=empty}
\caption{Fig. 3.1}
\end{table}
- Show that a suitable estimate for the value of \(\mu\) is 5.1.
Fig. 3.2 shows part of a screenshot for a \(\chi ^ { 2 }\) test to assess the goodness of fit of a Poisson model. The sample mean has been used as an estimate for the population mean. Some of the values in the spreadsheet have been deliberately omitted.
\begin{table}[h]
| A | B | C | D | E |
| \includegraphics[max width=\textwidth, alt={}]{e8624e9b-5143-49d2-9683-cc3a1082694e-4_132_40_1069_273} | Number of wasps | Observed frequency | Poisson probability | Expected frequency | Chi-squared contribution |
| 2 | \(\leqslant 2\) | 7 | 0.1165 | 6.9887 | 0.0000 |
| 3 | 3 | 5 | | 8.0874 | 1.1786 |
| 4 | 4 | 12 | | | 0.2765 |
| 5 | 5 | 10 | | | 0.0255 |
| 6 | 6 | 10 | 0.1490 | 8.9400 | 0.1257 |
| 7 | 7 | 11 | 0.1086 | 6.5134 | 3.0904 |
| 8 | \(\geqslant 8\) | 5 | 0.1440 | 8.6414 | |
| 9 | | | | | |
\captionsetup{labelformat=empty}
\caption{Fig. 3.2}
\end{table} - Determine the missing values in each of the following cells, giving your answers correct to 4 decimal places.
- C3
- D5
- E8
- Explain why some of the frequencies have been combined into the categories \(\leqslant 2\) and \(\geqslant 8\).
- In this question you must show detailed reasoning.
Carry out the hypothesis test at the 5\% significance level. - Jane also carries out a \(\chi ^ { 2 }\) test for the number of wasps leaving another nest. As part of her calculations, she finds that the probability of no wasps leaving the nest in a 5 -second period is 0.0053 . She finds that a Poisson distribution is also an appropriate model in this case.
Find a suitable estimate for the value of the mean number of wasps leaving the nest per 5-second period.