A marine biologist conducted a study to investigate whether a species of sea turtle displays a preference for nesting site lighting conditions (dark beaches vs artificially lit beaches) and whether these nests successfully hatch (hatch vs fail to hatch).
Below is the partial table of observed and expected frequencies used to calculate a Chi-square statistic.
Calculate the expected frequency for cell D (Artificially Lit / Fail). Present your answer to two decimal places and show your workings.
| Cell | Observed frequency (OOO) | Expected frequency (EEE) | O−EO - EO−E | (O−E)2(O - E)^2(O−E)2 | (O−E)2/E(O - E)^2 / E(O−E)2/E |
|---|---|---|---|---|---|
| A (Dark / Hatch) | 28 | 21.84 | 6.16 | 37.95 | 1.74 |
| B (Dark / Fail) | 14 | 20.16 | -6.16 | 37.95 | 1.88 |
| C (Artificially Lit / Hatch) | 11 | 17.16 | -6.16 | 37.95 | 2.21 |
| D (Artificially Lit / Fail) | 22 |
Formula for χ2\chi^2χ2:
χ2=∑(O−E)2E \chi^2 = \sum \frac{(O - E)^2}{E} χ2=∑E(O−E)2513 exam-style questions on OCR A Level Psychology Data recording, analysis and presentation. Each one has a worked solution and a mark scheme showing where the marks go.