Starfish coildots is a disease affecting approximately 40 different species of sea stars and several other echinoderms. A sample of 240 ochre starfish and 155 sunflower starfish found that 97 ochre starfish and 54 sunflower starfish showed signs of infection.
Is there evidence to suggest that the difference in the proportion of infected ochre starfish is greater than the proportion of infected sunflower starfish?
(a) Define the parameter(s) of interest using the correct notation. Then, state the null and alternative hypotheses for this study.
(b) Calculate the observed test statistic and state the distribution it follows (including degrees of freedom, if needed).
(c) Give the p-value, or a range of appropriate values for the p-value.
(d) Using the significance level α = 0.10, state your conclusions regarding the proportion of infected starfish in a plain English sentence.
(e) Determine the 90% confidence interval for the difference in the proportions of infected ochre starfish and sunflower starfish (ochre - sunflower). Does your answer here agree with your answer in Part (d)? Explain.
Is there evidence to suggest that the difference in the proportion of infected ochre starfish is greater than the proportion of infected sunflower starfish?
(a) Define the parameter(s) of interest using the correct notation. Then, state the null and alternative hypotheses for this study.
(b) Calculate the observed test statistic and state the distribution it follows (including degrees of freedom, if needed).
(c) Give the p-value, or a range of appropriate values for the p-value.
(d) Using the significance level α = 0.10, state your conclusions regarding the proportion of infected starfish in a plain English sentence.
(e) Determine the 90% confidence interval for the difference in the proportions of infected ochre starfish and sunflower starfish (ochre - sunflower). Does your answer here agree with your answer in Part (d)? Explain.