An A student of the author earned grades of 63, 91, 88, 84, and 79 on her five regular statistics tests. She earned grades of 86 on the final exam and 90 on her class projects.
Her combined homework grade was 70. The five regular tests count for 60% of the final grade,
the final exam counts for 10%, the project counts for 15%, and homework counts for 15%. What
is her weighted mean grade? What letter grade did she earn (A, B, C, D, or F)? Assume that a
mean of 90 or above is an A, a mean of 80 to 89 is a B, and so on.
to be censored at the current time that this list was compiled.) If you use the values in Data Set 15
and ignore the presidents who are still alive, what is the mean? If you use the values given in Data
Set 15 along with the additional values of 37+, 25+, 21+, 13+, and 5+, what do we know about
the mean? Do the two results differ by much?
37. Trimmed Mean Because the mean is very sensitive to extreme values, we say that it is not
a resistant measure of center. By deleting some low values and high values, the trimmed mean
is more resistant. To find the 10% trimmed mean for a data set, first arrange the data in order,
then delete the bottom 10% of the values and delete the top 10% of the values, then calculate
the mean of the remaining values. Use the axial loads (pounds) of aluminum cans listed below
(from Data Set 30 “Aluminum Cans” in Appendix B) for cans that are 0.0111 in. thick. An axial
load is the force at which the top of a can collapses. Identify any outliers, then compare the
median, mean, 10% trimmed mean, and 20% trimmed mean.
247 260 268 273 276 279 281 283 284 285 286 288
289 291 293 295 296 299 310 504
38. Harmonic Mean The harmonic mean is often used as a measure of center for data sets
consisting of rates of change, such as speeds. It is found by dividing the number of values n by
the sum of the reciprocals of all values, expressed as
n
a x
1
(No value can be zero.) The author drove 1163 miles to a conference in Orlando, Florida. For
the trip to the conference, the author stopped overnight, and the mean speed from start to finish
was 38 mi>h. For the return trip, the author stopped only for food and fuel, and the mean speed
from start to finish was 56 mi>h. Find the harmonic mean of 38 mi>h and 56 mi>h to find the
true “average” speed for the round trip.
33. The mean is 3.14. Yes!
34. The mean is 81.2 = B35a