代写ECON 83A: STATISTICS FOR ECONOMIC ANALYSIS MIDTERM #1 2019代做Python程序
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MIDTERM #1 — FEBRUARY 13, 2019
MULTIPLE CHOICE QUESTIONS [18 PTS]
1. Some hotels ask their guests to rate the hotel’s services as excellent, very good, good, and poor. This is an example of the
a) ordinal scale.
b) ratio scale.
c) nominal scale.
d) interval scale.
2. Income is an example of a variable that uses the
a) ratio scale.
b) interval scale.
c) nominal scale.
d) ordinal scale.
3. A histogram is
a) a graphical representation of a frequency or relative frequency distribution.
b) a graphical method of presenting a cumulative frequency or a cumulative rela- tive frequency distribution.
c) the history of data elements.
d) the same as a pie chart.
4. The numbers of hours worked (per week) by 400 statistics students are shown below.
Number of hours Frequency
0–9 20
10–19 80
20–29 200
30–39 100
The cumulative percent frequency for students working less than 20 hours per week is
a) 20%.
b) 25%.
c) 80%.
d) 100%.
5. The geometric mean of 8 and 12 has a value of
a) 20.
b) √20.
c) √96.
d) 96.
6. If two groups of numbers have the same mean, then
a) their standard deviations must also be equal.
b) their medians must also be equal.
c) their modes must also be equal.
d) other measures of location need not be the same.
7. The pth percentile is a value such that approximately
a) p percent of the observations are less than the value and (100 - p) percent are more than this value.
b) p percent of the observations are less than the value and p percent are more than this value.
c) (100 - p) percent of the observations are less than the value and p percent are more than this value.
d) (100 - p) percent of the observations are less than the value and (100 - p) per- cent are more than this value.
8. The weights (in pounds) of a sample of 36 individuals were recorded and the following statistics were calculated.
mean = 160 range = 60
mode = 165 variance = 324
median = 170
The coefficient of variation equals
a) 0.1125%.
b) 11.25%.
c) 203.12%.
d) 0.20312%.
9. The numerical value of the standard deviation can never be
a) larger than the variance.
b) zero.
c) negative.
d) smaller than the variance.
10. The coefficient of correlation
a) is the same as the coefficient of determination.
b) can be larger than 1.
c) cannot be larger than 1.
d) cannot be negative.
11. The collection of all possible sample points in an experiment is
a) the sample space.
b) an event.
c) a combination.
d) the population.
12. If A and B are independent events with P(A) = 0.65 and P(A ∩ B) = 0.26, then
P(B) =
a) 0.400.
b) 0.169.
c) 0.390.
d) 0.650.
13. Each customer entering a department store will either buy or not buy some merchandise. An experiment consists of following 3 customers and determining whether or not they purchase any merchandise. The number of sample points in this experiment is
a) 2. b) 4. c) 6. d) 8.
14. If A and B are mutually exclusive events with P(A) = 0.3 and P(B) = 0.5, then P(A ∩ B) =
a) 0.30.
b) 0.15.
c) 0.00.
d) 0.20.
15. If P(A) = 0.45, P(B) = 0.55,and P(A [ B) = 0.78,then P(A j B) =
a) 0.00.
b) 0.45.
c) 0.22.
d) 0.40.
16. The probability of at least one head in two flips of a coin is
a) 0.25.
b) 0.33.
c) 0.50.
d) 0.75.
17. Revised probabilities of events based on additional information are
a) joint probabilities.
b) posterior probabilities.
c) marginal probabilities.
d) complementary probabilities.
18. The complement of P(A j B) is
a) P(AC j B).
b) P(A j BC).
c) P(B j A).
d) P(A ∩ B).
PROBLEM SOLVING QUESTIONS [42 PTS]
Problem 1. (14 pts) Global Engineers hired the following number of Class 1 engi- neers during the first six months of the past year. (Assume the data represents a sample.)
Month No. of Hires
January 3
February 2
March 4
April 2
May 6
June 0
a) Determine the mean, the median, the mode, and the range for the monthly num- bers of hired engineers. (6 pts)
b) Compute the variance and the standard deviation. (3 pts)
c) Compute the first and the third quartiles. (3 pts)
d) Compute the z-scores for the months of May and June. (2 pts)
Problem 2. (10 pts) The following data represent the daily supply (y in thousands of units) and the unit price (x in dollars) for a product.
Daily Supply (y) Unit Price (x)
4 2
5 3
9 8
15 8
7 5
a) Compute and interpret the sample covariance for the above data. (4 pts)
b) Compute the variance for the daily supply. (2 pts)
c) Compute the variance for the unit price. (2 pts)
d) Compute and interpret the sample correlation coefficient. (2 pts)
Problem 3. (8 pts) An applicant has applied for positions at Company A and Com- pany B. The probability of getting an offer from Company A is 0.4, and the proba- bility of getting an offer from Company B is 0.3. Assuming that the two job offers are independent of each other, what is the probability that
a) the applicant gets an offer from both companies? (2 pts)
b) the applicant will get at least one offer? (2 pts)
c) the applicant will not be given an offer from either company? (2 pts)
d) Company A does not offer her a job, but Company B does? (2 pts)
Problem 4. (10 pts) A statistics professor has noted from past experience that (i) a student who follows a program of studying at least two hours for each hour in class has a probability of 85% of getting a grade of B or better, (ii) a student who follows a program of studying one hour for each hour in class has a probability of 55% of getting a grade of B or better, while (iii) a student who does not follow a regular study program has a probability of 25% of getting a grade of B or better. It is known that 30% of the students study at least two hours for each hour in class, 65% of the students study one hour for each hour in class, and 5% of the students do not study regularly.
a) What is the probability that a randomly selected student has earned a grade of B or better? (4 pts)
b) Find the probability that a student who has earned a B or better grade studied at least two hours for each hour in class. (2 pts)
c) Find the probability that a student who has earned a B or better grade studied one hour for each hour in class. (2 pts)
d) Find the probability that a student who has earned a B or better grade did not study regularly. (2 pts)