Homework for Section 7.2
In questions 1, 2 and 3, each table gives the results from two independent random samples from two
populations called A and B.
Find the standard error of the difference for each one.
1.
n
f8e5
X
s
A
100
73
20
B
200
68
18
2.
n
f8e5
X
s
A
25
12.3
1.5
B
25
10.9
2.0
3.
n
f8e5
X
s
A
12
88
30
B
10
100
25
For questions 4, 5 and 6,
a. State the question as a claim about the difference between two
population means (in words).
b. Write Ha and Ho in symbols.
Say what your symbols stand for.
4. Are children who repeat a grade shorter, on the average, than those who do not?
A study compared
the average height of 86 boys who had repeated a grade to the average height of 1300 boys who had
not repeated.
5. Do students perform better, on the average, when the early questions on an exam are easy?
Researchers gave two independent groups of students different exams.
One exam had easy questions
at the beginning and the other had hard questions at the beginning.
Both exams ended with five
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 Spring '08
 Staff
 Statistics, Normal Distribution, Probability, Standard Error, average age, average height, Arthroscopy

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