Grey Kangaroos are large, social marsupials, indigenous to Australia. The Eastern Greys are a light grayish brown, while the Western Grey is a copper brown color. As part of a study of the development of these creatures, biologists have measured various aspects of their skeletal structure. A sample of 148 palate widths was taken from skeletal remains and the data is presented in the stem-and-leaf plot below. The distributions of skeletal measures are generally thought to be approximately normal, which is consistent with the stem-and-leaf plot for this sample. The display uses five lines for each stem. Thus, "2t|" is the stem for palate widths of 22 and 23, "2f|" for 24 and 25, "2s|" for 26 and 27, and so on. (The "t" then stands for leaves that are twos and threes, the "f" for leaves of fours and fives, etc.) The mean palate width of this sample is 2.6 cm, and the standard deviation is 0.3 cm.

Palate Width - Grey Kangaroos 1|0 = 1 cm N = 124 1.| 1t| 1f| 1s|77 1*|89 2.|01111111111 2t|222222222223333333333333 2f|444444444444444455555555555555 2s|6666666666667777777 2*|88888888888889999999999999 3.|0000011 3t|223 3f| 3s| 3*| 

a) if this sample is a good representation of the population of Grey Kangaroos, approximate what percent of palate widths in this sample would exceed 2.9 cm?

b) What is the approximate percentile of a palate width that is 2.0 cm?

c) One measure of variability is the length of an interval that contains the middle 90% of the values of a distribution. For these data, how long is that interval?