chapter three-text

Question 1

central tendency

Answer 1

a statistical measure to determine a single score that defines the center of a distribution; representative of the entire group

Question 2

formula for the population mean

Answer 2

μ = (ΣX)/N
add all scores in the population, then divide by N=number of scores in the population

Question 3

formula for the sample mean

Answer 3

sample mean = M - (ΣX)/n
n=number of scores in the sample

Question 4

formula for the overall mean

Answer 4

overall mean = M = (ΣX₁+ΣX₂) / (n₁+n₂)

Question 5

a population of N=5 scores has a mean of μ=12. what is ΣX for this sample?
a. 12/5=2.4
b. 5/12=0.417
c. 5*12=60
d. cannot be determined

Answer 5

a. 5*12=60

Question 6

a sample has a mean of M=72. if one person with a score of X=98 is removed from the sample, what effect will it have on the sample mean?
a. the sample mean will increase
b. the sample mean will decrease
c. the sample mean will remain the same
d. cannot be determined

Answer 6

b. the sample mean will decrease

Question 7

one sample of n=4 scores has a mean of M=10, and a second sample of n=10 has a mean of M=20. if the two samples are combined, then what value will be obtained for the mean of the combined sample?
a. equal to 15
b. greater than 15 but less than 20
c. less than 15 but more than 10
d. none of the above

Answer 7

b. greater than 15 but less than 20

Question 8

for the following frequency distribution table, what are the values for ΣX and n?
x = 4, 3, 2, 1
f = 1, 2, 3, 4
a. 20; 4
b. 10; 10
c. 20; 10
d. 10; 2

Answer 8

c. 20; 10

Question 9

a population of N=10 scores has a mean of 30. if every score in the distribution is multiplied by 3, then what is the value of the new mean?
a. still 30
b. 33
c. 60
d. 90

Answer 9

d. 90

Question 10

median

Answer 10

the midpoint of the list

Question 11

formula for the median (if there are two middle scores)

Answer 11

median=(x+y)/2
x-middle score 1
y-middle score 2

Question 12

formula for the fraction

Answer 12

(number needed to reach 50%) / (number in the interval)

Question 13

what is the median for the following set of scores?
scores: 1, 6, 8, 19
a. 6
b. 6.5
c. 7
d. 7.5

Answer 13

c. 7

Question 14

what is the median for the sample presented in the following frequency distribution table?
x = 4, 3, 2, 1
f = 1, 2, 2, 3
a. 1.5
b. 2.0
c. 2.5
d. 3.0

Answer 14

b. 2.0

Question 15

find the precise median for the following scores measuring a continuous variable.
scores: 1, 4, 5, 5, 5, 6, 7, 8
a. 5
b. 5.17
c. 5.67
d. 6

Answer 15

b. 5.17

Question 16

mode

Answer 16

the score or category that has the greatest frequency

Question 17

for the sample shown in the frequency distribution table, what is the mode?
x = 5, 4, 3, 2, 1
f = 1, 4, 3, 4, 5
a. 4
b. 2
c. 2.5
d. 1

Answer 17

d. 1

Question 18

if the mean, median, and mode are all computed for a distribution of scores, which of the following statements cannot be true?
a. no one had a score = to the mean
b. no one had a score = to the median
c. no one had a score = to the mode
d. none of the above

Answer 18

c. no one had a score = to the mode

Question 19

what is the mode for the following set of n=8 scores?
scores: 2, 4, 4, 5, 7, 8, 8, 8
a. 4
b. 5
c. 5.5
d. 8

Answer 19

d. 8

Question 20

for a distribution of scores, the mean = the median. what is the most likely shape of this distribution?
a. symmetrical
b. pos skewed
c. neg skewed
d. none of the above

Answer 20

a. symmetrical

Question 21

for a pos skewed distribution with a mode of x=20 and a median of x=25, what is the most likely value for the mean?
a. greater than 25
b. less than 20
c. between 20 and 25
d. none of the above

Answer 21

a. greater than 25

Question 22

for a pos skewed distribution, what is the most probable order for the three measures of central tendency from smallest to largest?
a. mean, median, mode
b. mean, mode, median
c. mode, mean, median
d. mode, median. mean

Answer 22

d. mode, median. mean

Question 23

a researcher is measuring the problem-solving times for a sample of n=20 lab rats. however, one of the rats fails to solve the problem so the researcher has an undetermined score. what is the best measure of central tendency for these data?
a. the mean
b. the median
c. the mode
d. none of the above

Answer 23

b. the median

Question 24

what is the best measure of central tendency for an extremely skewed distribution of scores?
a. the mean
b. the median
c. the mode
d. none of the above

Answer 24

b. the median

Question 25

one item on a questionnaire asks students to identify their preferred animal or the school mascot from three different choices. what is the best measure of central tendency for the data from this question?
a. the mean
b. the median
c. the mode
d. none of the above

Answer 25

c. the mode