Radioactive lichen. Lichen has a high absorbance capacity for radiation fallout from nuclear accidents. Since lichen is a major food source for Alaskan caribou, and caribou are, in turn, a major food source for many Alaskan villagers, it is important to monitor the level of radioactivity in lichen.

Researchers at the University of Alaska, Fairbanks, collected data on nine lichen specimens at various locations for this purpose. The amount of the radioactive element cesium-137 was measured (in microcuries per milliliter) for each specimen. The data values, converted to logarithms, are given in the following table (note that the closer the value is to zero, the greater is the amount of cesium in the specimen).

Location Bethel -5.50 -5.00 Eagle Summit -4.15 -4.85 Moose Pass -6.05 Turnagain Pass -5.00 Wickersham Dome -4.10 -4.50 -4.60

a. Construct a dot plot for the nine measurements.

b. Construct a stem-and-leaf display for the nine measurements.

c. Construct a histogram plot of the nine measurements.

d. Which of the three graphs in parts a–c, respectively, is most informative?

e. What proportion of the measurements has a radioactivity level of -5.00 or lower?