A lab scientist is interested in whether lab rats that grow up alone grow as lar
ID: 2947359 • Letter: A
Question
A lab scientist is interested in whether lab rats that grow up alone grow as large as lab rats that grow up with other rats around them to play with. He randomly selects 10 young rats with approximately the same age and size. Five of these will spend the next four months by themselves and the other five rats will each have three other rats to play with during that same time. After four months, the scientist measures the abdomen circumference of all the rats (in mm). The results are shown below:
Alone group (#1)
110
123
113
103
120
Play group (#2)
119
125
131
128
136
What are the hypotheses to test whether the rats grow up to be equally large or whether the playing rats grow up larger?
A.
H0: ?1 = ?2 versus Ha: ?1 < ?2
B.
H0: ?1 = ?2 versus Ha: ?1 > ?2
C.
H0: ?1 = ?2 versus Ha: ?1 ? ?2
D.
H0: ?1 < ?2 versus Ha: ?1 = ?2
(C is incorrect)
Alone group (#1)
110
123
113
103
120
Play group (#2)
119
125
131
128
136
Explanation / Answer
We need to test whether the rats grow up to be equally large or whether the playing rats grow up larger. Hence, the correct hypotheses will be:
H0: ?1 = ?2 versus Ha: ?1 < ?2
Option A is correct.
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