This preview shows pages 1–3. Sign up to view the full content.
QUIZ 4 (CHAPTER 7)
SOLUTIONS
MATH 119 – SPRING 2011 – KUNIYUKI
105 POINTS TOTAL, BUT 100 POINTS = 100%
Do not
leave “+”, “
±
”, or
“
±
” in your final confidence intervals; write the lower
limit and the upper limit of each interval, as we have done in class. Avoid rounding
until you write the simplified margin of error or your final answer. Then, round to
the same number of decimal places as the given value of
x
,
s
, or
s
2
. If you want to
round in the middle of a problem, round to at least five significant digits.
(We're assuming that the population of interest is much larger than the sample, so there is no need to use a finite
population correction factor. Do not
use continuity corrections.)
1)
We will conduct a survey to estimate the average number of gifts purchased by
American families the day after Thanksgiving. We want to have 92%
confidence that the resulting sample mean will be within 0.3 gifts of the true
population mean. Assuming that the population standard deviation is 3.7 gifts
(based on a similar survey conducted last year), how many families should be in
the sample? Use the formula:
n
=
z
±
/2
²
E
³
´
µ
¶
·
¸
2
¹
º
º
º
»
¼
¼
¼
(8 points)
Find the critical values (CVs) for a 92% confidence interval. The negative CV is about
±
1.75 (actually, it is between
±
1.75 and
±
1.76). Therefore, the positive CV,
z
, is
about 1.75. (Note that 1.76 would be the more conservative choice.)
n
=
1.75
()
3.7
0.3
±
²
³
´
µ
¶
2
·
¸
¸
¸
¸
¹
º
º
º
º
, or, conservatively,
=
466 families
·
»
¹
¼
n
=
1.76
3.7
0.3
±
²
³
´
µ
¶
2
·
¸
¸
¸
¸
¹
º
º
º
º
=
472 families
·
»
¹
¼
This preview has intentionally blurred sections. Sign up to view the full version.
View Full Document2)
The Barry Bonds Exercise Company is testing a new piece of exercise
equipment in its standard mode. The company wants to know about the lengths
of time that adult American males can endure on the equipment. Assume that
This is the end of the preview. Sign up
to
access the rest of the document.
 Spring '11
 staff
 Math, Statistics

Click to edit the document details