Answer Happy

3. Darwin suggested that plants pollinated by long-tongued insects would benefit by having long flowers, because greater length would cause the long-tongued insects to press themselves further into the flower to reach the nectar, increasing the chance that pollen is removed and that pollen from other flowers is received. Some plants have evolved "nectar spurs"-long projections off the back of the flowers that have the nectar at the bases. Several populations of the South African orchid, Disa draconis, evolved longer nectar spurs after switching pollinators from relatively short-tongued horseflies to long-tonged tanglewing flies. To measure the advantage of the long spurs, researchers randomly selected 59 flowers and shortened the length of their spurs. They randomly selected another 59 flowers to serve as controls. One week later, the numbers of flowers that had received pollen on their stigmas were recorded for each group. Ten of the 59 flowers with shortened Spurs had received pollen, whereas 27 of the 59 control flowers had received pollen. a. Is this an experimental or an observational study, and WHY? (1 point for the why part) b. Calculate the odds ratio to test whether having longer spurs is associated with increased chance of receiving pollen. 12 points) c. The confidence interval for the odds ratio was 1.8< OR < 9.9. Clearly state your conclusion and how you came to that conclusion. If there is an association, include the direction of the association between variables in your answer (2 points) d. What is the best estimate of the probability that a shortened spur receives pollen in the population of flowers? [1 point)
c. Clearly state the null and alternate hypotheses you would use to test whether there is a significant correlation between tail and wing length. You don't need to use complete sentences, but you must use numbers in your answer. [2 points) d. Conduct a formal test of your hypotheses for part c, above. (2 points) e. After conducting the above test correctly, you obtain a P value of 0.001. Clearly state your conclusion and how you came to that conclusion. [2 points total) f. Assume we were interested in determining whether we could predict tail length from wing length. 1) Draw a CIRCLE around the data point that would yield the largest residual value. (1 point) ii) Draw a SQUARE around a data point that would yield a residual value close to zero but negative. [1 point)