Homework Answers for chapter 7 exercises 8, 14, 20, 26, 30, 46, 50, 58, 60 and 61
8. a.
b.
c. Answers will vary, below is one sample
Sample
Sample Values Sum
1 2,3,2,3,3 12 2.6
2 3,3,4,2,4 16 3.2
3 3,3,4,4,2 16 3.2
4 3,2,5,5,3 18 3.6
5 3,4,4,2,7 20 4.0
d. Sample mean is very close to the population mean. It is not to be expected that they are exact.
e. There is less
dispersion in the sample means than the population.
14.
a.
$18.775 and $21.225, found by
b.
The confidence interval is based on the standard error computed by
. As n,
the sample size, increases (in this case from 49 to 64) the standard error
decreases and the confidence interval becomes smaller.
20. a. 0.15, found by 30/200
b.
0.101 and 0.199, found by
26.
60, found by
30.
a.
5718, found by
b.
Increase the allowable error from 0.01 to, say, 0.05.
Thus the sample size would be reduced to 229, found by
46.
2.55 up to 2.97 meals, found by
50.
0.647 and 0.753, found by
Note that the finite-population correction factor (FPC) was not applied because n/N is less than 0.05. It is more accurate to use the FPC, but it should not reduce the standard error much in this case.
58.
97, found by
60. a. 708.13, rounded up to 709, found by: 0.21(1 – 0.21)[1.96/0.03]2
b. 1068, found by 0.50(0.50)[1.96/0.03]2
61. a. 25%, found by 25/100
b.
A 95% confidence interval for the proportion of employees who will NOT
use the ATM: 0.172 to 0.328, found by
Can Huntington be sure that at least 40 percent of the employees of Fun Toy
Company will use the ATM? That is, can we say that AT MOST 60 percent will NOT
use the ATM? (The book says "No, 0.40 not in interval," but this is
incorrect.) We can be confident that the proportion who will not use the
ATM is less than 60 percent. Therefore, at least 40 percent will use the ATM,
probably much more.
c. 1.65, found by 165/100
d.
1.387 to 1.913, found by
Note:
s = 1.4659
e. No, because 0 is not in the interval between 1.387 and 1.91.