Doplhin Activity

Use this diagram to show that bar charts of within-group proportions are easier to compare than bar charts of raw frequencies.

Is the proportion feeding higher in the morning or at noon?

Is the morning bar higher only because the total number dolphin groups observed in the morning was higher?

Select Propn within Time of day. The bar chart for each time is scaled to have the same total (1.0).

Finally, select Activity under the horizontal axis. This clusters the bars by the types of activity and makes it easier to compare the proportions.

  • A bigger proportion of dolphins Travel in the middle of the day than in morning or evening.
  • The dolphins were rarely Feeding in the afternoon.
  • The dolpnins rarely did Social activities in the evening.

Groups of dolphins were observed off the coast of Iceland near Keflavik in 1998. The data here give the time of the day and the main activity of the group, whether travelling quickly, feeding or socializing. The diagram below shows the number of groups observed at each time of day, categorised by activity type.