Question

Groups of dolphins were observed off the coast of Iceland near Keflavik in 1998. The data in the file dolphin_dat on the course website give the time of the day and the main activity of the group, whether travelling quickly, feeding, or socializing. The dolphin groups varied in size. Usually feeding or socializing groups were larger than travelling groups. (Sec. 8.2)

Source of data: Marianne Rasmussen, Department of Biology, University of Southern Denmark, Odense, Denmark.

Activity        Period  Groups
Travel  Morning  6
Feed    Morning 28
Social  Morning 38
Travel  Noon     6
Feed    Noon     4
Social  Noon     5
Travel  Afternoon       14
Feed    Afternoon        0
Social  Afternoon        9
Travel  Evening 13
Feed    Evening 56
Social  Evening 10

Refer to Exercise 1 above.

1. By hand, draw a bar graph depicting the sample proportion of dolphins feeding for the morning and evening periods. Add a whisker to the top of each bar to denote the standard error of the sample proportion.
2. Examine the bar graph you produced for part (a). Briefly comment on whether there appears to be a difference proportion.
3. Conduct the appropriate hypothesis test for a two-by-two contingency table and report the P-values for Fisher’s exact test and the asymptotic chi-square distribution approximation for this test. Compare these results with your answer to part (b) in Exercise 1.

Answer 1