[ answers in web view ]
As an aid for your study, here are a collection of questions similar to what
might show up on the midterm exam. The actual exam may be longer or shorter,
there may be some material on the exam that is not covered here, and there may
be some material here that doesn't show up on the exam. The coverage for the
exam is ch1-8 in our textbook.
The exam is in-class, 120min long, and you will enter your answers on the
computer. You may not use your personal computer or cellphone; all computer
use must be through the classroom PCs.
You may use Excel, the lecture notes, textbook, your own paper notes, your
own notes uploaded online, and any resource
on the Internet (including Google) that is not a live person.
You may not communicate in any way (including text message, email, chat, etc.)
with classmates or anyone outside of class; if you have a question, raise your
hand and I will help you as much as I can.
- A quality control inspector has rated each batch produced today on a scale
from A through E, where A represents the best quality and E is the worst.
What is the level of measurement of this variable?
Ordinal
- The process of using sample data to make an estimate about the population is called __________
Inference
- All 18 people in a department have just received across-the-board pay raised of 3%. What has happened to the standard deviation of salaries?
Also increased by 3%
- The table below shows sales of some “light” foods:
| "Light" Food | Sales ($Millions) |
|---|
| Entenmann's Fat Free baked goods | $125.5 |
| Healthy Request soup | $123.0 |
| Kraft Free processed cheese | $83.4 |
| Aunt Jemima Lite and Butter Lite pancake syrup | $58.0 |
| Fat Free Fig Newtons | $44.4 |
| Hellmann's Light mayonnaise | $38.0 |
| Louis Rich turkey bacon | $32.1 |
| Kraft Miracle Whip free | $30.3 |
| Ben & Jerry's frozen yogurt | $24.4 |
| Hostess Lights snack cakes | $19.3 |
| Perdue chicken/turkey franks | $3.8 |
| Milky Way II candy bar | $1.1 |
My company is planning to launch a new brand of light food. Our goal is to
reach at least the 20th percentile of current brands. What is our sales goal,
in dollars?
rank=2.4, round up to 3: 3rd entry is $19.3.
Or, using PERCENTILE(): $20.32.
The difference is due to
the different way Excel computes percentiles.
- Produce a relative frequency histogram for the variable "Airline" in the
dataset AirlinePassengers.xls
(linked).
- Using the same dataset from the preceding problem, produce a joint
frequency distribution for the two variables, "Male/Fem." and "Business or
Pleasure". Are these two variables independent in this dataset? Why or
why not?
No: e.g., P(Business | Male) ≠ P(Business | Female)
- Download the dataset Angry.xls.
What fraction of "Irritability" emotions were described as "Extreme"? (Enter as a decimal, e.g., 0.79.)
P(Extreme | Irritability) = 113/800 = 0.14125
- Download the dataset Hydronics.xls.
Considering the joint distribution of the two variables, "Product #1" and
"Product #2", find the observation which is the most likely to be an outlier
(deviates the most from the rest of the sample). What is the Product #2 value
for this outlier?
(Hint: what plot is most appropriate to show the joint distribution of these two variables?)
Scatter plot: fourth observation (row 5) has score of 9.1 on Product #2.
- You have followed up on people who received your catalog mailing. You
found that 4% of these people ordered the hat, and 6% ordered the mittens. Of
the people who ordered the hat, 55% also ordered the mittens. Of the people
who did not order the hat, what percentage ordered the mittens?
Given: P(H)=4%, P(M)=6%, P(M|H)=55%,
the question is looking for P(M|noH).
Then P(M and H) = (.04)(.55) = 2.2%.
Since P(M and H) and P(M and noH) must add up to P(M), so
P(M and noH) must equal 6% - 2.2% = 3.8%.
We are looking for P(M|noH), which is P(M and noH) / P(noH).
P(noH) must be 100% - P(H) = 96%, so
P(M|noH) = 3.8% / 96% = 3.958333%.
- In order to pay your firm’s debts this year, you will need to be awarded
at least 2 contracts. This is not usually a problem, since the yearly average
is 5.1 contracts. What is the probability that you will not earn enough to pay
your firm’s debts this year? (Hint: which distribution is appropriate?)
POISSON(1, 5.1, 1) = 3.72%
- (p.255 #41) The mean time between failures (MTBF) for a particular model
of power supply unit (PSU) is 4,000 hours. Some PSUs may fail earlier; some
later. What is the probability of a random PSU failing in less than 2,100
hours? (Hint: which probability distribution is appropriate?)
- A study indicates that 65% of workers report that they and/or their spouse have saved some money for retirement. If a random sample of 20 workers is taken, what is the probability that more than half of the workers (and/or their spouses) have saved for retirement? Enter your answer as a decimal.
1-BINOMDIST(10,20,0.65,1)