Refer to the American Journal of Physical Anthropology (Vol. 142, 2010) study of the dietary habits of extinct mammals, Exercise 3.25 (p. 130). Recall that 18 cheek teeth extracted from skulls of an extinct primate species discovered in western Wyoming were analyzed. Each tooth was classified according to degree of wear (unworn, slight, light-moderate, moderate, moderate-heavy, or heavy), with the 18 measurements shown in the accompanying table.
Data on Degree of Wear
Unknown ................................. Slight
Unknown ................................. Slight
Unknown ................................. Heavy
Moderate .............................. Unworn
Slight ........................... Light-moderate
Unknown ...................... Light-moderate
Moderate-heavy ..................... Moderate
Moderate ............................... Unworn
Slight .................................. Unknown
a. Suppose the researcher will randomly select one tooth from each wear category for a more detailed analysis. How many different samples are possible?
b. Repeat part a, but do not include any teeth classified as "unknown" in the sample.
c. If the tooth is selected at random, what is the probability it is not classified as "unknown"?