Review#1 for Test1, J. Dykacz, 2/2006

Circle the best answer. Identify the type of sample.

1) In order to find out how its employees felt about higher student fees imposed by the Board of Trustees, a university divided employees into three categories: staff, faculty, and student employees. A random sample was selected from each group; they were telephoned and asked for their opinions. This type of sampling procedure produces a

a) cluster sample

b) convenience sample

c) simple random sample

d) stratified sample

e) systematic sample

Circle the best answer. Identify the type of sample.

2) Parts are rolling off an assembly line, and a sample of parts is desired. A starting part is picked at random, and every 50^th part is selected for the sample. This sample is an example of a

a) cluster sample

b) convenience sample

c) simple random sample

d) stratified sample

e) systematic sample

3) Identify the type of sampling described by the following sentences.

The population is divided into sections or groups. Some groups are randomly selected, and all members of those selected groups are chosen for the sample.

___________________________________

4) If a distribution is ______________________, the mean, median, and the mode are the same.

5) If a histogram of test scores has two distinct peaks, then the distribution of test scores is __________________.

6 ) Circle the letter(s) corresponding to all statements which are true.

a) If the standard deviation is 4, the variance is 16.

b) The symbol for the population standard deviation is s.

c) The standard deviation is always positive.

d) The smaller the standard deviation, the more variable the scores in a dataset.

7) Let x = number of ounces of chocolate a person receives for Valentine's Day. X is measured for Essex students. If the third quartile is 10 ounces, what percent of the students receive less than 10 ounces of chocolate? ________

8) A population of male weights is normally distributed with a mean of 170 lbs. and a standard deviation of 10 pounds. Find the z-score corresponding to a weight of 155 lbs.

z = __________

9) A researcher would like to know if she can predict a person’s annual income at age 40 from his/her college GPA. (Assume that everyone in the population of interest has gone to college.)

The explanatory variable is __________________________________.

The outcome variable is __________________________________.

10) A researcher gathers information for a certain type of automobile by sampling automobiles and finding the age of the vehicle in years (x) and the price in units of one thousand dollars (y). The regression equation is = –2x + 20. Assume a straight line is appropriate.

If an auto is 4 years old, what is the predicted average price in dollars? ___________

11) Circle all statements which are TRUE about the linear correlation coefficient, r.

a) r falls between –1 and 1 (can be –1 or 1)

b) r may sometimes be zero

c) r can never be greater than 2

d) the sign of r is different from the sign of the slope of the linear regression line

e) If the points of a scatter plot all lie on a line which goes up (as you move from left to right),

r = -1

?OMIT12) Experiment: tossing one fair, regular die

Event A is the event of getting a number greater than or equal to 2

Event B is the event of getting a number less than 4

Find P(A or B) = __________

?OMIT13) Experiment: tossing one fair, regular die

Event A is the event of getting a number which is at least 3

Event B is the event of getting a number less than 3

Are events A and B mutually exclusive? ____ You must briefly explain.

14) Male heights are normally distributed with a mean of 67 inches and a standard deviation of 3 inches.

John has a height of 70 inches.

What is his z-score? _____________

Is his height unusual? (yes/no) ________

15) A teacher conducts a study relating the grade on a test and the number of hours of sleep before the test. Based on her random sample, the following equation is obtained. Note: x = number of hours of sleep the night before and y = grade on the test.

y = 4x + 40

What is the slope of this line? _______

Interpret the slope. Be specific.

16)A boxplot is drawn for a group of test scores. If Q₁=70, Q₃=85, and the median=80, what percent of the test scores are less than 85?

17) Let x = amount of lead found in a person's blood measured in suitable units and y = the person's IQ (intelligence). Assume that a representative sample of people is taken from a population, and the equation of the line of best fit (i.e. the regression line) is y = -2x + 100.

What is the slope of this line? ______

Interpret the slope. Be specific.

?OM IT18)Which of the following numbers could be probabilities?

1.4 6/5 -70% -2.3

19) Given a set of 20 test scores. If the minimum is 45, the maximum is 98, the median is 80, Q₁ is 75, and Q₃ is 90, what is the IQR (Interquartile Range)?___________

ANSWERS

1) d	10) $12,000
2) e	11) a, b, c
3) cluster sampling	12) 6/6=1
4) normal or bell-shaped or Gaussian	13) Yes – The events have no outcome in common.
	14) +1, No- Not greater than +2 or less than -2
5) bimodal 6) a, b	15) 4, As the number of hours of sleep increases by 1 hour, the average predicted grade increases by 4 points.
7) 75%	16) 75%
8) –1.5	17) –2, As the amount of lead in the blood increases by 1 unit, the average predicted IQ decreases by 2 points.
9) college GPA, annual income	18) none of these numbers 19) 15 (90-75)