# Once upon a time, I had a fast-food lunch with a mathematician colleague

1.

(10 points) Once

upon a time, I had a fast-food lunch with a mathematician colleague. I noticed

a very strange behavior in him. I called it the Au-Burger Syndrome since it was

discovered by me at a burger joint. Based on my unscientific survey, it is a rare

but real malady inflicting 2% of mathematicians worldwide. Yours truly has

recently discovered a screening test for this rare malady, and the finding has

just been reported to the International Association of Insane Scientists (IAIS)

for publication. Unfortunately, my esteemed colleagues who reviewed my

submitted draft discovered that the reliability of this screening test is only

80%. What it means is that it gives a positive result, false positive, in 20%

of the mathematicians tested even though they are not afflicted by this

horribly-embarrassing malady.

I

have found an unsuspecting victim, oops, I mean subject, down the street. This

good old mathematician is tested positive! What is the probability that he is

actually inflicted by this rare disabling malady?

2.

(5 points) Most

of us love Luzon mangoes, but hate buying those that are picked too early.

Unfortunately, by waiting until the mangos are almost ripe to pick carries a

risk of having 15% of the picked rot upon arrival at the packing facility. If

the packing process is all done by machines without human inspection to pick

out any rotten mangos, what would be the probability of having at most 2 rotten

mangos packed in a box of 12?

3. (5 points)

We have 7 boys and 3 girls in our church choir. There is an upcoming concert in

the local town hall. Unfortunately, we can only have 5 youths in this

performance. This performance team of 5 has to be picked randomly from the crew

of 7 boys and 3 girls.

a. What is the probability that all 3 girls are picked

in this team of 5?

b. What is the probability that none of the girls are

picked in this team of 5?

c. What is the probability that 2 of the girls are

picked in this team of 5?

4.

(10 points) In

this economically challenging time, yours truly, CEO of the Outrageous Products

Enterprise, would like to make extra money to support his frequent

**-and-double-lobster-tail**

*filet-mignon*dinner habit. A promising enterprise is to mass-produce tourmaline wedding

rings for brides. Based on my diligent research, I have found out that women's

ring size normally distributed with a mean of 6.0, and a standard deviation of

1.0. I am going to order 5000 tourmaline wedding rings from my reliable Siberian

source. They will manufacture ring size from 4.0, 4.5, 5.0, 5.5, 6.0, 6.5, 7.0,

7.5, 8.0, 8.5, 9.0, and 9.5. How many wedding rings should I order for each of

the ring size should I order 5000 rings altogether? (

*Note: It is natural to*

assume that if your ring size falls between two of the above standard

manufacturing size, you will take the bigger of the two.)

assume that if your ring size falls between two of the above standard

manufacturing size, you will take the bigger of the two.

5.

(5 points) A soda company want to stimulate sales in this economic climate by

giving customers a chance to win a small prize for ever bottle of soda they

buy. There is a 20% chance that a customer will find a picture of a dancing

banana () at the bottom of the cap upon opening up a bottle of soda. The

customer can then redeem that bottle cap with this picture for a small prize.

Now, if I buy a 6-pack of soda, what is the probability that I will win

something, i.e., at least winning a single small prize?

6. (5 points) When constructing

a confidence interval for a population with a simple random sample selected

from a normally distributed population with unknown σ, the Student

*t*-distribution

should be used. If the standard normal distribution is correctly used instead,

how would the confidence interval be affected?

7. (10 points) Below is a

summary of the Quiz 1 for two sections of STAT 225 last spring. The questions

and possible maximum scores are different in these two sections. We notice that

Student

*A4*in Section A and Student

*B2*in Section B have the same

numerical score.

8. (5 points) My brother wants

to estimate the proportion of Canadians who own their house. What sample size

should be obtained if he wants the estimate to be within 0.02 with 90%

confidence if

a. he uses an estimate of 0.675

from the Canadian Census Bureau?

b. he does not use any prior

estimates? But in solving this problem, you are actually using a form of

"prior" estimate in the formula used. In this case, what is your

"actual" prior estimate? Please explain.

9. (5 points) An amusement park

is considering the construction of an artificial cave to attract visitors. The

proposed cave can only accommodate 36 visitors at one time. In order to give

everyone a realistic feeling of the cave experience, the entire length of the

cave would be chosen such that guests can barely stand upright for 98% of the

all the visitors.

The mean height of American men

is 70 inches with a standard deviation of 2.5 inches. An amusement park

consultant proposed a height of the cave based on the 36-guest-at-a-time

capacity. Construction will commence very soon.

The park CEO has a second

thought at the last minute, and asks yours truly if the proposed height is

appropriate. What would be the proposed height of the amusement park

consultant? And do you think that it is a good recommendation? If not, what

should be the appropriate height? Why?

10. (5 points) A department

store manager has decided that dress code is necessary for team coherence. Team

members are required to wear either blue shirts or red shirts. There are 9 men

and 7 women in the team. On a particular day, 5 men wore blue shirts and 4

other wore red shirts, whereas 4 women wore blue shirts and 3 others wore red

shirt. Apply the

*Addition Rule*to determine the probability of finding

men

**blue shirts in the team.**

*or*

*Please refer to the*

following information for Question 11 and 12.following information for Question 11 and 12.

It is an open secret that

airlines overbook flights, but we have just learned that bookstores

**underbook**

(I might have invented this new term.) textbooks in the good old days that

we had to purchase textbooks.

To make a long story short,

once upon a time, our UMUC designated virtual bookstore, MBS Direct, routinely,

as a matter of business practice, orders less textbooks than the amount

requested by UMUC's Registrar's Office. That is what I have figured out.......

Simply put, MBS Direct has to "eat" the books if they are not sold.

Do you want to eat the books? You may want to cook the books before you eat

them! Oops, I hope there is no account major in this class?

OK, let us cut to the

chase..... MBS Direct believes that only 85% of our registered students will

stay registered in a class long enough to purchase the required textbook. Let's

pick on our STAT 200 students. According to the Registrar's Office, we have 600

students enrolled in STAT 200 this spring 2014.

11. (10 points) Suppose you are

the CEO of MBS Direct, and you want to perform a probability analysis. What

would be the number of STAT 200 textbook bundles you would order so that you

stay below 5% probability of having to back-order from Pearson Custom

Publishing? (

*Note: Our Provost would be very angry when she hears that*

textbook bundles have to be back-ordered.In any case, we no longer need

textbook bundles have to be back-ordered.

the service of MBS Direct as we are moving to 100% to free

*eResources*.

*Auf*

Wiedersehen, MBS Direct......)

Wiedersehen

**IMPORTANT: Yes, you may use**

technology for tacking Question 11

technology for tacking Question 11

12. (5 points) Is there an

approximation method for Question 11? If so, please tackling Question 11 with

the approximation method.

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