Your supervisor has a theory that sex ratios in the eggs of certain species of crocodile depends on the temperature at which they are incubated. Her rival at a big American university is sure that egg sex ratio is determined by humidity, but your supervisor is a strong opponent of this idea.

1)      On her instruction, you collect 23 eggs, and incubate 12 of them at a low humidity and 11 of them at a high humidity.  You find that 3 of the 12 are male and 8 of the 11 are male. You run the appropriate test to test whether there is a difference in male-female proportion (make sure you do it!) and your supervisor wants to know what p-value you get. You tell her. She is overjoyed and asks you to start writing a paper entitled ‘Humidity does not affect crocodile egg sex ratio’. What do you say to her?

2)      Later, you conduct an experiment incubating eggs at a range of temperatures. Unfortunately only three or four eggs fit in each incubator at a time, and it is very difficult to get each incubator to be exactly the same temperature. Luckily you have access to lots of incubators! So you put three or four eggs in each incubator, record the actual temperature for each incubator, and for each egg you record whether it ends up male or female. You find that each incubator actually ended up at a different temperate, but the range of temperatures achieved in the incubators covered the range of temperatures that you are interested in. When you discuss the analysis with your supervisor, she assumes that you will calculate the proportion of males for each incubator, and then conduct a one-way ANOVA to test whether proportion of males varies with temperature. What do you say to her?

3)      Later, you tell her that also measured the actual humidity in each incubator, and after conducting an appropriate analysis, you got the results summary below. When she sees the summary, she is again overjoyed and asks you to start writing a paper entitled ‘Temperature affects crocodile egg sex ratio, but humidity does not’. What do you say to her?

For this part of the written reflective assignment you need to write for each of the three responses to your supervisor. Clearly indicate where you are responding to each of the three points using numbers.

While you are encouraged to be polite to your supervisor of course, you should also be confident that you may know more about modern statistical ideas and methods than your supervisor (who is an excellent biologist, but hasn’t studied statistics for many many years, and who did ANOVAs with pen and paper when she last did). If you disagree with your supervisor, you should clearly and concisely explain to her why, and what you think would be better, and why it would be better. If you agree with her, then you should also explain why, and suggest any possible improvements. All answers must be fully in your own words. You may use references to support your arguments, but they are not required. You will still get full marks for a very clear and convincing answer that does not use references but demonstrates full understanding of the issues in your own words, and you will receive no marks for an answer that is referenced but demonstrates no understanding of the issues in your own words. You will be penalised for irrelevant points.