Suppose that monthly sales volume for a product is normally distributed, with a mean of 500 units and a standard deviation of 50 units. If x denotes the number of units sold in a month, what are the following probabilities:
1) P(x < 450)
2) P(x > 600)
3) P(400 < x < 450)
4) What is the probability that during one particular minute there will be more than 6 phone calls?
5) What is the probability that during one particular minute there will be less than 5 phone calls?
6) What is the probability of observing 30 or more heads in 50 flips?
7) What is the probability of observing more than 35 tails in 50 flips?
8) How many questions should the student expect to get correct on this exam?
9) What is the probability that the student will get a "C" or better, which is 14 or more correct?
10) What is the probability that the student will score lower than a "C" (13 or less correct)?
11) What is the probability of no false-positives for this week's test?
12) What is the probability of at least 1 false-positive for this week's tests?
13) What is the likelihood that the test will give 5 to 10 false positives?
14) What is the chance of at most 3 false positives?
15) How many false positives should the company expect?
16) Given that the passing score is 65, approximately what percentage of students passes the first exam?
17) What is the probability that the student will score an "A" on the exam? (A score of 90 or more)
18) The middle 95% of the scores will tend to fall between _________ and ________.
19) Two coins are tossed, at the same time, find the probability that two heads are obtained.
a. ½
b. ¼
c. ¾
d.
20) Two dice are rolled, at the same time, find the probability that the sum is equal to 1.
a. 0
b.
c. ½
d. ¼
21) A jar contains 3 red marbles, 7 green marbles and 10 white marbles. If a marble is drawn from the jar at random, what is the probability that this marble is white?
a. 3/20
b. 7/20
c. 1/2
d. 17/20
e. 13/20
The next two questions refer to the following situation. The following list of Uniform
Resource Locators (URLs) contains some of the most visited sites on the World Wide
Web.
URL Hits (millions)/day
www.yahoo.com 12.5
www.msn.com 11.8
www.passport.com 6.3
www.hotmail.com 6.2
www.aol.com 5.1
www.netscape.com 3
www.iwon.com 2.9
www.excite.com 2.6
www.ebay.com 2.6
www.lycos.com 2.4
22) Based on the above data, what is the average and standard deviation, respectively?
a. 3.54, 3.60
b. 4.05, 3.60
c. 5.54, 3.79
d. 3.54, 3.79
e. 4.05, 10.1
23) Based on a graph of the above data, what is the shape?
a. Symmetric
b. Symmetric
c. Left-skewed
d. Right-skewed
e. Left-skewed
The distribution of the salaries of 100 employees at a small consulting firm is displayed in the following histogram. Suppose 95% of the data falls between 33 and 77.
24) Based on the empirical rule, what is the standard deviation of this sample of data?
a. 121
b. 22
c. 11
d. 5.5
e. 44
Consider the survey question "How much time does the chief executive officer spend at work?"
25) What type of data would this question collect?
a. Numerical, interval
b. Binomial
c. Categorical
d. Normal
e. Numerical, continuous
The manager of a small restaurant wishes to determine how long the average customer had to wait to be served during the lunch hour. At the lunch hour on a particular typical day, 10 customers experienced the following waiting times (in minutes):
7.5, 10.6, 10.2, 7.5, 5.3, 5.1, 10.0, 8.7, 4.0, 9.6
26) What is the shape of this data?
a. Right skewed
b. Binomial
c. Approximately symmetric
d. Left skewed
e. Normal
The following random sample of annual salaries was recorded. Units are in thousands of dollars.
50, 52, 48, 46, 32, 51, 47, 20, 53, 49
27) What are values of the average and median, respectively?
a. 48.5, 51
b. 44.8, 44.8
c. 48.5, 46
d. 44.8, 36.5
e. 44.8, 48.5
28) Stem-and-Leaf Display
12 | 0
13 | 1 3 7 7
14 | 2 4 5
15 |
16 | 9 9
17 | 0 9
18 | 4
19 | 1 4
20 | 7
What is the shape of the data?
a. Normal
b. Left-skewed
c. Right-skewed
d. Approximately symmetric
e. Uniform