Edexcel IAL Biology 6P.5 Uncertainty, errors and conclusions

The photograph shows a young locust eating the leaves of a plant.

Locusts can breed in large numbers and destroy crops, such as sorghum, in East Africa. A scientist observed that some varieties of sorghum were more likely to be eaten by young locusts. The scientist collected the seeds of two varieties of sorghum (A and B) and grew them in trays. Locust eggs were collected and hatched into young locusts. Twenty young locusts were placed in a cage containing 100 g of fresh sorghum leaves of variety A. The cage was kept at $30^{\circ} \mathrm{C}$. After 24 hours, the leaves were removed and the mass of leaves eaten was calculated. This method was repeated with fresh sorghum leaves of variety B. The method was repeated six times for these two varieties of sorghum leaves. The results: Mass of leaves eaten of variety A 17.317.217.517.016.716.9 Mass of leaves eaten of variety B 17.817.917.717.617.817.4

The student analysed the data using the t test formula:

Where: $\overline{\mathrm{x}}$ is the mean value for each treatment n is the number of samples for each treatment $\left(\mathrm{S}_{\mathrm{A}}\right)^{2}=0.084$ and $\left(\mathrm{S}_{\mathrm{B}}\right)^{2}=0.032$

The table shows the critical values of t for different degrees of freedom. The number of degrees of freedom $=\left(n_{1}-1\right)+\left(n_{2}-1\right)$. Describe the conclusions that can be drawn from this investigation. Use the information in the table to support your answer.