A+ Answers



Question 1

A jar contains 10 red marbles and 30 blue marbles.  What is the probability of randomly selecting a red marble from the jar?

Select one:

 a. 10/40

 b. 10/30

 c. 1/10

 d. 1/40

Question 2

A normal distribution has a mean of µ = 100 with  = 20.  If one score is randomly selected from this distribution, what is theprobability that the score will have a value between X = 90 and X = 110?

Select one:

 a. 0.6915

 b. 0.3830

 c. 0.1915

 d. 0.3085

Question 3

A normal distribution has a mean of µ = 100 with  = 20.   If one score is randomly selected from this distribution, what is theprobability that the score will have a value between X = 80 and X = 100?

Select one:

 a. 0.1587

 b. 0.3413

 c. 0.8413

 d. 0.6826

Question 4

A normal distribution has a mean of µ = 70 with  = 12.   If one score is randomly selected from this distribution, what is theprobability that the score will be less than X = 76?

Select one:

 a. 0.1915

 b. 0.3085

 c. 0.6915

 d. 0.3830

Question 5

A normal distribution has µ = 80 and  = 10.   What is the probability of randomly selecting a score greater than 90 from this distribution?

Select one:

 a. p = 0.1587

 b. p = 0.6915

 c. p = 0.3085

 d. p = 0.8413

Question 6

A random sample of n = 4 scores is selected from a population.  Which of the following distributions definitely will be normal?

Select one:

 a. Neither the sample, the population, nor the distribution of sample means will definitely be normal.

 b. The scores in the sample will form a normal distribution.

 c. The distribution of sample means will form a normal distribution.

 d. The scores in the population will form a normal distribution.

Question 7

A researcher conducts an experiment to determine whether moderate doses of St. Johns Wort have any effect of memory for college students.  For this study, what is the independent variable?

Select one:

 a. The amount of St. Johns Wort given to each participant

 b. The group of college students

 c. This cannot be answered without more information.

 d. The memory score for each participant

Question 8

A researcher is curious about the average monthly cell phone bill for high school students in the state of Florida.  If this average could be obtained, it would be an example of a ____.

Select one:

 a. statistic

 b. parameter

 c. population

 d. sample

Question 9

A researcher records the change in weight (gain or lost) during the first semester of college for each individual in a group of 25 freshmen, and calculates the average change in weight.  The average is an example of a ____.

Select one:

 a. variable

 b. parameter

 c. constant

 d. statistic

Question 10

A researcher uses an anonymous survey to investigate the study habits of American college students.  Based on the set of 56 surveys that were completed and returned, the researcher finds that these students spend an average of 4.1 hours each week working on course material outside of class. For this study, the average of 4.1 hours is an example of a ____.

Select one:

 a. statistic

 b. population

 c. sample

 d. parameter

Question 11

A sample has M = 72 and s = 4.  In this sample, what is the X value corresponding to z = -2.00?

Select one:

 a. X = 60

 b. X = 68

 c. X = 64

 d. X = 70

Question 12

A sample of n = 100 scores is selected from a population with  = 80 with  = 20.  On average, how much error is expected between the sample mean and the population mean?

Select one:

 a. 2 points

 b. 0.8 points

 c. 4 points

 d. 0.2 points

Question 13

A sample of n = 25 scores has M = 20 and s2 = 9.  What is the sample standard deviation?

Select one:

 a. 4.5

 b. 9

 c. 3

 d. 81

Question 14

A sample of n = 4 scores has a mean of M = 8.  If one new score with a value of X = 3 is added to the sample, what will be the value for the new mean?

Select one:

 a. M = 8.75

 b. M = 8

 c. It cannot be determined with the information provided.

 d. M = 7

Question 15

A sample of n = 9 scores has a standard error of 6.  What is the standard deviation of the population from which the sample was obtained?

Select one:

 a. 6

 b. 18

 c. 2

 d. 54

Question 16

 Remove flag

Figure 2-2

What is the shape for the distribution shown in the accompanying graph?

Select one:

 a. positively skewed

 b. symmetrical

 c. normal

 d. negatively skewed

Question 17



Figure 2.1

For the distribution in the accompanying graph, what is the value of X?

Select one:

 a. 21

 b. 30

 c. 15

 d. cannot be determined

Question 18

For a particular population a sample of n = 4 scores has an expected value of 10.  For the same population, a sample of n = 25 scores would have an expected value of ____.

Select one:

 a. 8

 b. 10

 c. 4

 d. 20

Question 19

For a population with a standard deviation of  = 6, what is the z-score corresponding to a score that is 12 points above the mean?

Select one:

 a. z = 12

 b. z = 6

 c. z = 2

 d. z = 1

Question 20

For a research study, comparing attitude scores for males and females, participant gender is an example of what kind of variable?

Select one:

 a. an independent variable

 b. a quasi-independent variable

 c. a quasi-dependent variable

 d. an dependent variable

Question 21

For the distribution in the following table, what is the 90th percentile?

X           c%

9         100%

8           80%

7           50%

6           25%

Select one:

 a. X = 8

 b. X = 9.5

 c. X = 8.5

 d. X = 9

Question 22

For the distribution in the following table, what is the 90th percentile?

X            c%

30-34   100%

25-29     90%

20-24     60%

15-19     20%

Select one:

 a. X = 24.5

 b. X = 29.5

 c. X = 29

 d. X = 25

Question 23

For the distribution in the following table, what is the percentile rank for X = 7?

X           c%

9         100%

8           80%

7           50%

6           25%

Select one:

 a. X = 37.5%

 b. X = 65%

 c. X = 50%

 d. X = 80%

Question 24

For the following distribution of quiz scores, How many individuals had a score of X = 2?

X    f

5    6

4    5

3    5

2    3

1    2

Select one:

 a. 5

 b. 3

 c. cannot be determined

 d. 1

Question 25

For the following distribution, what is the highest score?

X         f

20-25   2

15-19   5

10-14   4

5-9       1

Select one:

 a. 20

 b. 25

 c. cannot be determined

 d. 5

Question 26

For the following frequency distribution of exam scores, how many students had scores lower than X = 80?

X          f

90-94    3

85-89    4

80-84    5

75-79    2

70-74    1

Select one:

 a. 2

 b. 3

 c. cannot be determined

 d. 7

Question 27

For the following frequency distribution of quiz scores, how many individuals took the quiz?

X    f

5    6

4    5

3    5

2    3

1    2

Select one:

 a. cannot be determined

 b. n = 21

 c. n = 15

 d. n = 5

Question 28

If an entire population with  = 60 and  = 8 is transformed into z-scores, then the distribution of z-scores will have a mean of ____ and a standard deviation of ____.

Select one:

 a. 60 and 8 (unchanged)

 b. 0 and 8

 c. 60 and 1

 d. 0 and 1

Question 29

If sample variance is computed by dividing SS by df = n – 1, then the average value of the sample variances from all the possible random samples will be ____ the population variance.

Select one:

 a. larger than

 b. unrelated to

 c. exactly equal to

 d. smaller than

Question 30

If the following scores were placed in a stem and leaf display, how many leaves would be associated with a stem of 6?

Scores: 26, 45, 62, 11, 21, 55, 66

64, 55, 46, 38, 41, 27, 29

36, 51, 32, 25, 34, 44, 59

Select one:

 a. 1

 b. 2

 c. 3

 d. 4

Question 31

In a population of scores, X = 83 corresponds to z = -0.50 and X = 93 corresponds to z = +2.00.  What are the values for the population mean and standard deviation?

Select one:

 a. = 81 and  = 6

 b. = 85 and  = 4

 c. = 85 and  = 2

 d. = 81 and  = 4

Question 32

In a population with  = 8, a score of X = 44 corresponds to a z-score of z = -0.50.  What is the population mean?

Select one:

 a.  = 40

 b.  = 52

 c.  = 48

 d.  = 36

Question 33

In a sample of n = 6 scores, the smallest score is X = 3, the largest score is X = 10, and the mean is M = 6.  If the largest score is changed from X = 10 to X = 22, then what is the value of the new mean?

Select one:

 a. The mean is still M = 6.

 b. The mean is M = 7.

 c. It is impossible to determine from the information given.

 d. The mean is M = 8.

Question 34

One sample has n = 4 scores and M = 10.  A second sample has n = 6 scores and M = 5.  If the two samples are combined, then what is the mean for the combined sample?

Select one:

 a. 70/6 = 11.67

 b. It cannot be determined with the information given.

 c. 70/4 = 17.5

 d. 70/10 = 7

Question 35

The average verbal SAT score for the entire class of entering freshmen is 530.  However, if you select a sample of 20 freshmen and compute their average verbal SAT score you probably will not get exactly 530.  What statistical concept is used to explain the natural difference that exists between a sample mean and the corresponding population mean?

Select one:

 a. parametric error

 b. sampling error

 c. statistical error

 d. inferential error

Question 36

The students in a psychology class seemed to think that the midterm exam was very easy. If they are correct, what is the most likely shape for the distribution of exam scores?

Select one:

 a. symmetrical

 b. normal

 c. negatively skewed

 d. positively skewed

Question 37

There is a six-point difference between two sample means.  If the two samples have the same variance, then which of the following values for the variance would make the mean difference easiest to see in a graph showing the two distributions.

Select one:

 a. s2 =  8

 b. s2 =  2

 c. s2 =  16

 d. s2 =  64

Question 38

What frequency distribution graph is appropriate for scores measured on a nominal scale?

Select one:

 a. only a bar graph

 b. only a polygon

 c. only a histogram

 d. either a histogram or a polygon

Question 39

What is the first step to be performed in the following mathematical expression?  (X)2

Select one:

 a. Square each score.

 b. Add the squared scores.

 c. Square the sum of the scores.

 d. Add the scores.

Question 40

What is the mode for the population of scores shown in the frequency distribution table?

X    f

5     1

4     2

3     3

2     4

1     2

Select one:

 a. 3.5

 b. 4

 c. 2

 d. 3

Question 41

What is the value of (X)2 for the following scores?  Scores: 1, 5, 2

Select one:

 a. 16

 b. 10

 c. 30

 d. 64

Question 42

What is the value of (X + 1) for the following scores?  Scores: 2, 4, 7

Select one:

 a. 10

 b. 16

 c. 13

 d. 11

Question 43

What is the value of (X – 2 )2 for the following scores?  Scores: 2, 3, 5

Select one:

 a. 8

 b. 16

 c. 36

 d. 10

Question 44

What is the value of SS (sum of squared deviations) for the following population?

Population:  2, 3, 0, 5

Select one:

 a. 13/4 = 3.25

 b. 38/4 = 9.50

 c. 13

 d. 38

Question 45

What is the value of SS for the following set of scores?  Scores:  1, 1, 4, 0

Select one:

 a. 18

 b. 9

 c. 6

 d. 10

Question 46

What is the variance for the following population of scores?  Scores:  5, 2, 5, 4

Select one:

 a. 6

 b. 2

 c. 1.22

 d. 1.5

Question 47

What term is used to describe the shape of a distribution in which the scores pile up on the lefthand side of the graph and taper off to the right?

Select one:

 a. symmetrical

 b. positively skewed

 c. normal

 d. negatively skewed

Question 48

What z-score value separates the top 70% of a normal distribution from the bottom 30%?

Select one:

 a. z = -0.52

 b. z = 0.84

 c. z = -0.84

 d. z = 0.52

Question 49

You are instructed to subtract four points from each score and find the sum of the resulting values.  How would this set of instructions be expressed in summation notation?

Select one:

 a. 4 – X

 b. X – 4

 c.  (X – 4)

 d. (4 – X)

Question 50

You have a score of X = 65 on an exam.  Which set of parameters would give you the best grade on the exam?

Select one:

 a.  = 60 and  = 5

 b.  = 60 and  = 10

 c.  = 70 and  = 5

 d.  = 70 and  = 10