Program into a second semester japanese language

program into a second-semester Japanese language course in an effort
to improve students’ Japanese reading comprehension ( Reading in a
Foreign Language , April, 2004). The professors collected 266 books
originally written for Japanese children and required their students to
read at least 40 of them as part of the grade in the course. The books
were categorized into reading levels (colour coded for easy selection)
according to length and complexity. Fourteen students participated in
the program. The number of books actually read by each student and
the student’s grade in the course are listed in the table below.
Grades
A B C
53 42 40 40 28 21 22
# of books 39 34 34 20 16
30 24
(a) Find the mean and standard deviation of the number of books
read by students who earned an A grade. Find the z -score for an
A student who read 40 books. Interpret the result.
(b) Find the mean and standard deviation of the number of books
read by students who earned either a B or a C grade. Find the
8

z -score for a B or C student who read 40 books. Interpret the
result.
(c) Refer to parts (a) and (b). Which of the two groups of students
is more likely to have read 40 books? Explain.
(2.192) Estimating the age of glacial drifts. Tills are glacial drifts con-
sisting of a mixture of clay, sand, gravel, and boulders. Engineers from
the University of Washington’s Department of Earth and Space Sci-
ences studied the chemical makeup of buried tills in order to estimate
the age of the glacial drifts in Wisconsin ( American Journal of Sci-
ence , January, 2005). The ratio of the elements aluminum (AI) and
beryllium (Be) in sediment is related to the duration of burial. The
AI–Be ratios for a sample of 26 buried till specimens are given in the
accompanying table and saved in the TILL file.
9