Stats Paper

Topics: Random variable, Standard deviation, Arithmetic mean Pages: 7 (1882 words) Published: November 1, 2011
1. A sample of 20 employee’s salaries from a large company results in the following salaries (in thousands of dollars) for this year.
28 31 34 35 37 47 42 42 49 41 42 60 52 52 51 72 67 61 75 77. What is the interquartile range (in thousands) of this data set? (A) 21.5 (B) 10 (C) 50 (D) 23 (E) correct answer is not given 2. Please refer to the previous question.

Suppose each employee in the company receives $3,000 raise for next year. The interquartile range (IQR) of the salaries will:
(A) be unchanged (B) be multiplied by $3,000
(C) increase by $3,000 (D) decrease by $3,000
3. An HIV test has a 9% chance of indicating a false positive and 0.5% chance of indicating a false negative. This test is administered to a population of 1000 patients, 6 of whom are actually infected. If a patient is tested positive, what is the probability that he actually is infected?

(A) 0.93 (B) 0.83 (C) 0.063 (D) 0.0587
4. A study shows that employees that begin their work day at 9:00 a.m. vary their times of arrival uniformly from 8:40 a.m. to 9:30 a.m. The probability that a randomly chosen employee reports to work between 9:00 and 9:10 is:

(A) 40% (B) 20% (C)10% (D) 30% (E)16.7%
5. If A and B are events such that P(A) = 0.20, P(B) = 0.40. Assuming that A and B are independent, what is the probability that none of these two events occur? (A) 0.40 (B) 0.60 (C) 0.52 (D) 0.48

6. Suppose that the wages of workers for a given company are normally distributed with a mean of $15 per hour. When we consider the proportion of the workers earning more than $13 per hour, we see that:

(A) it is less than the proportion earning less than $13 per hour. (B) it is greater than the proportion earning less than $18 per hour. (C) it is less than 50%.
(D) it is less than the proportion earning more than the mean wage. (E) none of the above statements are correct.
7. An Introductory statistics class has 45 students. You want to call an SRS (simple random sample) of 5 students from the class to ask if they feel they’re well prepared for this exam. You label the students 01, 02,…, 45. Suppose that you enter a table of random digits at this line:

14459 26056 31421 40371 65103 62253 22490 61181
Your SRS contains the students labeled:
(A) 14, 45, 92, 60, 56
(B) 14, 31, 03, 10, 22
(C) 14, 03, 10, 22, 22
(D) 14, 45, 31, 42, 03
(E) 14, 45, 31, 42, 14
8. According to astrological tradition people with birthdays between September 23 and October 22, inclusive, are born under the Zodiac sign “Libra”. A randomly selected person was born in a non-leap year (365 day) year. What is the probability that she was born in October or is a “Libra”?

(A) 0.0603 (B) 0.1068 (C) 0.1671 (D) 0.2274 (E) 0.0000
9. The mean life of pair of shoes is 40 months with a standard deviation of 8 months. If the life of the shoes is normally distributed, how many pairs of shoes out of one million would we expect will need replacement before 36 months? (A) 500,000 (B) 808,500 (C) 191,500 (D) 308,500 (E) 705,100

10. The letter grade that you receive on this test (i.e. A, B, etc.) is an example of a(n): (A) nominative variable
(B) ordinal variable
(C) interval variable
(D) ratio variable
11. A particular characteristic of a unit of a population is an example of a(n): (A) variable
(B) observation
(C) measurement
(D) statistic
12. The weather office forecast and actual weather for London is summarized in the following table.
Rain No rain
Forecast: Rain 66 156
Forecast: No Rain 14
Total 80 1,000
What percentage of the time was the weather office correct?
(A) 6.6% (B) 76.4% (C) 83% (D) 92%
13. The _____________distribution would most likely be used to describe the distribution of arrivals to a grocery store and the _____________ distribution would most likely be used to describe the time between arrivals of customers to the grocery store.

(A) Binomial, Normal
(B) Poisson, Exponential
(C) Normal, Binomial
(D) Exponential, Poisson
(E) Binomial, Poisson
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