Self test midterm 1

3. Assume you have a distribution of scores that is approximately normally distributed. What proportion of scores can you expect to be between one standard deviation below the mean and one standard deviation above the mean? A. .68 B. .50 C. .95 D. .99

A. .68

10. The SS (sum-of-squares) for a set of scores is 80 based on a sample of size 21. Thus, s2 (the sample's estimate of sigma squared) for the scores is ____. A. 4 B. 2.0 C. 2 D. 16

A. 4

11. If the 57th percentile on an examination is 74, then A. 57 percent of the scores on the exam were 74 or less. B. 57 percent of the scores on the exam were 74 or higher. C. 43 percent of the scores on the exam were 74 or less. D. 43 percent of the scores on the exam were 74 or higher.

A. 57 percent of the scores on the exam were 74 or less.

8. For the set of three scores 3, 6, and 9, s2 (the sample's estimate of sigma squared) is ____. A. 9.0 B. 6.0 C. 4.0 D. 2.0

A. 9.0

4. In journal articles following the Publication Manual of the American Psychological Association style, the mean is usually indicated by the symbol ____. A. M B. xbar C. X D. Mn

A. M

12. Suppose you obtained the following distribution of scores of errors made by participants solving a difficult maze: 9, 9, 10, 12, 14, 17, 19, 20, 94. What would be the most appropriate descriptive measure of central tendency for this distribution? A. Median B. Mean C. Mode D. All the measures of central tendency would be equally appropriate.

A. Median

14. In journal articles following the Publication Manual of the American Psychological Association style, the standard deviation is usually represented by ____. A. SD B. S C. s D. σ

A. SD

15. If you see ____ on a graph, you should be concerned about the graph being misleading. A. a missing or awkward scale B. everything properly labeled C. bars D. categories

A. a missing or awkward scale

4. The relative frequency of a distribution is obtained by A. dividing the frequency of a score by the total number of scores in the distribution. B. dividing the total number of scores in a distribution by the frequency of a score. C. multiplying the frequency of a score by 100 D. multiplying the frequency of a score by the total number of scores in the distribution.

A. dividing the frequency of a score by the total number of scores in the distribution.

9. The ____ is the most frequently occurring score in a distribution of scores. A. mode B. median C. mean D. percentile

A. mode

12. A frequency polygon always indicates the frequencies A. on the Y axis. B. on the X axis. C. at the lower stated limit of a class interval. D. at the upper stated limit of a class interval.

A. on the Y axis.

12. The statement "The probability that X is equal to or greater than 25 and equal to or less than 56 is .34" is expressed in probability notation as_____. A. p(25 ≤ X ≤ 56) = .34 B. p(25 ≥ X ≤ 56) = .34 C. p(25 ≥ X ≥ 56) = .34 D. p(25 ≤ X ≥ 56) = .34

A. p(25 ≤ X ≤ 56) = .34

14. Suppose the mean salary for the employees of an organization is $95,000, whereas the median salary for these employees is $41,200. The distribution of salaries in this organization is A. positively skewed. B. negatively skewed. C. bimodal. D. unimodal.

A. positively skewed.

4. The symbol for the sample standard deviation used to estimate the population standard deviation is ____. A. s B. s2 C. σ D. σ2

A. s

15. You have collected a set of scores from subjects performing a reaction time task. You decide that the most appropriate measure of central tendency for the scores is the mean. The most appropriate measures of variability would thus be A. the standard deviation. B. the sample variance. C. biased. D. the range.

A. the standard deviation.

1. The symbol used to represent the sample mean is ____. A. xbar B. X C. Mdn D. Mn

A. xbar

5. The variance calculated from sample data and used to estimate the population variance is given by the formula ____. A. B. C. D.

B sigma (x-xbar)^2/N-1

6. The mean of a standard normal distribution is equal to ____ and its standard deviation is equal to ____. A. 1; 0 B. 0; 1 C. 1; 1 D. 100; 10

B. 0; 1

1. An instructor gave students a 20-item quiz on a course topic. The distribution of scores on the quiz was: 8, 8, 10, 10, 11, 12, 12, 13, 13, 13, 15, 15, 16, 17, 19, 19, 20, 20, 20. What is the range for these scores? A. 20 B. 12 C. 13 D. A range cannot be calculated for this set of scores.

B. 12

3. Suppose you obtained the following scores on three 10-item quizzes in one of your classes: 8, 9, 10. What is the sum of squares for these scores? A. 0 B. 2 C. 9 D. 1

B. 2

8. For a class interval of 40 to 44 in a grouped frequency distribution the lower real limit is ____. A. 39 B. 39.5 C. 40 D. 40.5

B. 39.5

9. The midpoint of the class interval of 40 to 44 in a grouped frequency distribution is ____. A. 41.5 B. 42 C. 42.5 D. 42.25

B. 42

7. A psychologist asked a group of people to remember a list of 20 names and then asked them to recall the names a week later. He found the following distribution of items recalled for 11 people: 5, 6, 7, 7, 7, 8, 9, 9, 13, 14, 15. The median for this set of scores is ____. A. 7 B. 8 C. 8.5 D. 9.1

B. 8

11. If s2 (the sample's estimate of sigma squared) for a set of scores is 81, then s for those scores is ____. A. 3 B. 9 C. (81)2 D. cannot be determined from the information given.

B. 9

13. If s = 0 for a distribution of scores, then which of the following is true? A. An error was made in the calculation because s cannot equal 0 B. All the scores in the distribution are equal to each other. C. The sample variance of the scores was equal to 10. D. The distribution was either positively or negatively skewed.

B. All the scores in the distribution are equal to each other.

2. The sample variance when divided by ____ is a biased estimate of the population variance. A. range B. N C. N - 1 D. median

B. N

15. Suppose an instructor returned an exam with standard scores in place of raw scores. For five students, the standard scores were: Jenn, +.54; Whitney, .00; Ramon, +1.21; Michelle, -.67; Clay, -.34. Based on these scores, ____ had the highest score on the exam, and ____ score was at the mean of the exam. A. Michelle; Clay's B. Ramon; Whitney's C. Whitney, Michelle's D. Ramon; Jenn's

B. Ramon; Whitney's

2. The simple frequency of scores in an ungrouped frequency distribution is indicated by ____. A. sf B. f C. F D. simfreq

B. f

1. If a distribution of scores is normally distributed, then the distribution can be completely described by A. its mean and range. B. its mean and standard deviation. C. finding the mode and median for the scores. D. its median and range.

B. its mean and standard deviation.

6. An instructor calculated a statistic on the scores of a biology exam so that as many students had a score above the value as students had a score below the value. This instructor calculated the A. mode. B. median. C. mean. D. unimode.

B. median.

8. Suppose you have a set of scores that are normally distributed with a mean equal to 90. The standard deviation for the scores is 15. If a score in the distribution is equal to 75, then the z for this score is ____. A. +1.0 B. +2.0 C. -1.0 D. -2.0

C. -1.0

11. A maker of breakfast cereal sponsors a contest. For each 100 cartons of cereal, 90 boxes contain a baseball rookie card, 5 boxes contain a package of chewing gum, 4 boxes contain a coupon worth half the price of another box of the cereal, and one box contains a coupon for a free box of the cereal. The boxes are randomly distributed to stores. If you buy a box of the cereal, what is the probability you will buy a box containing a half-price coupon? A. 4 B. .4 C. .04 D. .5

C. .04

4. Assume you have a distribution of scores that is approximately normally distributed. What proportion of scores fall between the mean and the highest value in the distribution? A. 1.00 B. .68 C. .50 D. .25

C. .50

14. If a set of scores is normally distributed with μ = 150 and σ = 15, what is the probability of a score being between 120 and 180? A. .50 B. .68 C. .95 D. .34

C. .95

9. If a population of scores is normally distributed and has a mean of 300 and a standard deviation of 50, then what proportion of scores would you expect to find between 200 to 400? A. .34 B. .68 C. .95 D. .99

C. .95

3. Which score has the highest simple frequency in the distribution below? X f 35 3 34 1 33 8 32 5 31 0 30 2 A. 36 B. 34 C. 33 D. 32

C. 33

9. Suppose σ = 7 for a population of scores. The variance for those scores is then ____. A. 7 B. 7 C. 49 D. 21

C. 49

10. An instructor gives students a 10-item multiple choice test. The distribution of scores was 4, 5, 5, 6, 6, 6, 7, 7, 7, 7, 7, 8, 8, 9, 9, 9, 10, 10 for 18 students. The mode for this distribution is __. A. 6 B. 6.5 C. 7 D. 7.5

C. 7

7. For a class interval of 72 to 76 in a grouped frequency distribution, the lower stated limit is ____. A. 71 B. 71.5 C. 72. D. 71.6

C. 72.

8. A characteristic of the median is that it A. cannot be calculated for a bimodal distribution. B. is the most frequently occurring score in a distribution of scores. C. is not affected by very extreme scores in the tails of a distribution. D. cannot be calculated if the number of scores in a distribution is an even number.

C. is not affected by very extreme scores in the tails of a distribution.

15. The sample mean is often reported as a measure of central tendency because it is A. easier to calculate than either the mode or median. B. more resistant to the effects of extreme scores than either the mode or median. C. more often used for inferential statistics than either the mode or median. D. not affected by a skewed distribution.

C. more often used for inferential statistics than either the mode or median.

5. Multiplying ____ by ____ provides the percentage frequency distribution. A. f; 100. B. rf; N C. rf; 100. D. (N - f); 100.

C. rf; 100.

14. When a distribution is bimodal, A. the majority of the scores are at the high end of the score range. B. the majority of the scores are at the low end of the score range. C. there are two scores that occur equally often with the highest frequency in the distribution. D. all scores occur approximately equally often.

C. there are two scores that occur equally often with the highest frequency in the distribution.

5. The mean of a population is represented by the symbol ____. A. X B. M C. μ D. X population

C. μ

6. ____ is the symbol for the population variance A. σ B. S^2 C. σ^2 D. s2

C. σ^2

13. If A and B are mutually exclusive outcomes in a probability distribution, and the p(A) = .30 and the p(B) = .20, then the p(A or B) equals ____. A. .10 B. .06 C. .60 D. .50

D. .50

5. A scientist obtained a normally distributed population of scores with a mean of 70 and a standard deviation of 10. What proportion of scores do you expect to find in the interval between 60 to 80? A. 1.00 B. .50 C. .34 D. .68

D. .68

6. The size of the class interval for a grouped frequency distribution can be found by A. using the formula (Xhighest + Xlowest) divided by the number of intervals desired. B. Subtracting the lowest score in a distribution from the highest score in a distribution. C. using the formula (72.5 Xhighest - Xlowest) divided by N D. .using the formula (Xhighest - Xlowest) divided by the number of intervals desired.

D. .using the formula (Xhighest - Xlowest) divided by the number of intervals desired.

2. A teacher observed the number of aggressive acts by five children over a one hour period in a child care center. She obtained the following set of scores: 7, 4, 4, 6, 4. What is the mean for this sample of scores? A. 4 B. 6 C. 3 D. 5

D. 5

12. Which of the following sets of scores would you expect to have the largest value of s? A. 5, 5, 6, 7, 7 B. 7, 7, 7, 7, 7 C. 5, 6, 7, 8, 9 D. 5, 5, 7, 9, 9

D. 5, 5, 7, 9, 9

7. For the set of three scores 3, 6, and 9, σ2 is ____. A. 1.0 B. 2.0 C. 3.0 D. 6.0

D. 6.0

10. The percentile rank of Jessica's score on a language exam was 73. This value indicates A. Jessica obtained a score of 73 out of 100 on the exam. B. 27 percent of the scores were less than Jessica's. C. 73 percent of the scores on the exam were equal to or greater than Jessica's. D. 73 percent of the scores were equal to or less than Jessica's.

D. 73 percent of the scores were equal to or less than Jessica's.

10. Suppose a student takes a standardized test measuring college level skills. Scores on the test are normally distributed with a mean of 500 and a standard deviation of 100. The student obtains a z score of 0.0 on the test. Which of the following statements is true of this person's score? A. The student received a score of zero on the test. B. The student's score is above the mean of 500. C. The student's score is below the mean of 500. D. The student scored 500 on the test.

D. The student scored 500 on the test.

2. The relative frequency under the normal distribution A. depends upon the shape of the distribution. B. depends upon the mean and variance of the distribution. C. is equal to 100. D. is equal to 1.0.

D. is equal to 1.0.

1. When listing the values for X in a simple frequency distribution it is important that you A. only list the values you feel are the most important. B. only list the values that have been observed. C. only list the ten most frequently observed values. D. list all possible values.

D. list all possible values.

11. A high school baseball coach created a distribution of hits by her players over five games. The distribution was 0, 1, 2, 2, 2, 3, 4, 5, 5, 5, 6, 7, 8, 8, 8 for 15 players. This distribution is A. non-modal. B. unimodal. C. bimodal. D. multimodal.

D. multimodal.

13. A ____ distribution would have a large number of high scores and only a few very low scores. A. normal B. bimodal C. positively skewed D. negatively skewed

D. negatively skewed

13. Suppose an experimenter obtained the scores 2, 4, 3, 6,10, 6. If a score of 98 were to be added to this distribution, it would most affect the value of A. the mode. B. the median. C. both the mode and median. D. the mean.

D. the mean.

3. Although s2 (sum-of-squares divided by N - 1) is a(n) ____ estimate of the population standard deviation, it is not reported as often as s because ____. A. biased; it is easier to calculate because the standard deviation is reported in units instead of squared units B. biased; it is easier to understand as the standard deviation is reported in units instead of squared units C. unbiased; the sample variance is always a biased estimator of the population variance D. unbiased; the standard deviation is simpler to interpret

D. unbiased; the standard deviation is simpler to interpret

7. Which of the following formulas would you use to convert a score from a normal distribution to a score on the standard normal distribution?

Z = X - mu / sigma