7.17 A group of 19 rats was divided randomly into two groups. The 12
animals in the experimental group lived together in a large cage fur-
nished with playthings that were changed daily, while the seven animals
in the control group lived in isolation without toys. Table E7.17 provides
the cortex weights (the thinking part of the brain) in milligrams. Use the
Wilcoxon test to compare the two populations.
TABLE E7.17
Experimental Group Control Group
707, 740, 745, 652, 649, 676,
699, 696, 712, 708, 749, 690669, 650, 651, 627,
656, 642, 6987.18 College students were assigned to three study methods in an experi-
ment to determine the e¤ect of study technique on learning. The three
methods are: read only, read and underline, and read and take notes.
The test scores are recorded in Table E7.18. Test to compare the three
groups simultaneously. Name your test and state clearly your null and
alternative hypotheses and choice of test size.
TABLE E7.18
Technique Test Score
Read only 15 14 16 13 11 14
Read and underline 15 14 25 10 12 14
Read and take notes 18 18 18 16 18 207.19 Four di¤erent brands of margarine were analyzed to determine the level
of some unsaturated fatty acids (as a percentage of fats; Table E7.19).
Test to compare the four groups simultaneously. Name your test and
state clearly your null and alternative hypotheses and choice of test size.
TABLE E7.19
Brand Fatty Acids (%)
A 13.5 13.4 14.1 14.2
B 13.2 12.7 12.6 13.9
C 16.8 17.2 16.4 17.3 18.0
D 18.1 17.2 18.7 18.47.20 A study was done to determine if simplification of smoking literature
improved patient comprehension. All subjects were administered a pre-
test. Subjects were then randomized into three groups. One group
received no booklet, one group received one written at the fifth-grade
278 COMPARISON OF POPULATION MEANS