Comparing tropical flowers: a contrast (optional). The data in Table 25.1 contain lengths for the bihai variety of Heliconia and for two forms (red and yellow) of the caribaea variety. We wonder (before looking at the data) whether the population mean for bihai differs from the average of the means for the two forms of caribaea.
(a) What contrast expresses this comparison?
(b) Give the null and alternative hypotheses for this comparison, find the sample contrast, and assess its statistical significance. What do you conclude?
(c) Give a 90% confidence interval for the population contrast in part (a).
