Question: Professor Williamson is investigating the different types of Iris plants. He has two samples of Irises (50 in each group) that he thinks represent different species. One of the things that would help him to prove this is if the plants are of different dimensions. He decides to look at the sepals and measure their lengths. If he can show that the lengths of the sepals are statistically significantly different he will have some evidence for his hypothesis. He conducts the following T test:

a.

b. What assumptions should Professor Williamson have evaluated? Where any of them met?

c. What are the null and the alternate hypotheses (2 tail) for the T test?

d. Interpret the results in terms of the hypotheses in your own words. Does Professor Williamson have evidence that might make him think that he has 2 species of irises?

e. What, in you own words, would happen if Professor Williamson made a type 1 error?

What would be a type II error?

Which of these could have occurred in this case?