An experiment was conducted on mice to determine whether two forms of iron, Fe-3+
and Fe-4+, are retained differently in the body. 18 mice were randomly assigned
to each of the two groups. The mice were given the iron orally, which was radio-
actively labeled so that the initial amount and the amount still retained after
a certain period of time could be measured.

Data are the percentages of iron retained in each mouse after the specified time
period. Is there a higher retention for one kind of iron? A higher retention is
desired for iron used as a human dietary supplement.

Data are from:

Rice J (1987). Mathematical Statistics and Data Analysis.

Data were reproduced in:

Ramsey and Schafer (1997). The Statistical Sleuth: A course in methods
of data analysis, Duxbury Press.