Fall 2011
FORM A
Name
Last:_____________________
First:
______________________
Exam 2:
Ch. 4, 5, 6, 7
Class Time
___________________
Directions:
• Put your NAME and CLASS TIME on THIS EXAM and on your SCANTRON.
• Put your NAME and CLASS TIME on your SCANTRON
.
• Write FORM A on your SCANTRON.
•
Each question has exactly one BEST answer.
There are 21 questions.
•
You may write on this exam.
There is no scratch paper allowed.
•
Each question is worth 5 points for a total of 105 points. This includes 5 bonus points!
•
If you have no note page, you must write NO NOTES
on your SCANTRON.
•
Put your SCANTRON and page of NOTES inside your EXAM when you turn it in.
When your exam is returned, you will get back all materials you turned in.
•
TURN YOUR CELL PHONE OFF.
Any noise from a cell phone will signal that your exam is over.
FAILURE TO FOLLOW ALL THE ABOVE INSTRUCTIONS WILL COST YOU THE 5
BONUS POINTS.
_________________________________________________________________________________
Questions 1 – 3 refer to the following:
A lumber yard cuts fence posts in lengths that follow a normal distribution with a mean length of 62.5
inches and a standard deviation of 1.2 inches.
1.
A fence builder needs fence posts that are at least 60 inches long.
What percent of fence posts are long enough for this builder to be able to use them?
A.
48.13%
B.
1.86%
C.
96.00%
D.
98.14%
2. The longest 15% of fence posts are at least how long?
3.
If samples of 9 fence posts are selected, find the probability that the sample average length is less
than 62 inches.
4.
A fabric manufacturer produces rolls of fabric that have occasional flaws in the weaving.
The distance between flaws (in meters) follows an exponential distribution with a mean of
3.5 meters.
Find the probability that the distance to the next flaw in the fabric is less than 2 meters.
Form A Page 1
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5.
At a birthing center, the midwives find that there are an average of 2 births every day.
Find the
probability that tomorrow there are exactly 4 births at the birthing center.
A.
0.1465
B.
0.8571
C.
0.0902
D.
0.9473
6.
Given X~N(8,5).
Suppose that the X value for each item in this population is decreased by 2.
Which of the following is true about the new distribution of X?
Questions 7 – 9 refer to the following:
http://www.gallup.com/poll/149558/SignificantlyFewerYearOlds
A recent study showed that the more young adults in the U.S. have health insurance since the new
healthcare law began allowing young adults age 1826 to stay on their parents' plans.
A Gallup Poll Survey shows that 75.8% of young adults in the U.S. have health insurance.
Suppose a random sample of 32 young adults in this age group in the U.S. are selected.
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 Fall '11
 Plum
 Math, Statistics, Normal Distribution, Standard Deviation, Scantron

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