Question 1

The 50th percentile is also called the median quartile.

Accepted Answer

A) True 
 B)False

Question 2

One reason the denominator for sample variance is (n - 1)is because this makes it an unbiased estimator of the population variance.

Accepted Answer

A) True 
 B)False

Question 3

Adding or subtracting the same constant to each score will not change the standard deviation.

Accepted Answer

A) True 
 B)False

Question 4

For nonnormal distributions,99.7% of data will fall within three standard deviations of the mean.

Accepted Answer

A) True 
 B)False

Question 5

A main disadvantage of computing a range is that it takes into consideration only two values regardless of the number of scores in a distribution.

Accepted Answer

A) True 
 B)False

Question 6

A researcher selects a sample of 24 participants and has them complete a survey on dating preferences.In this example,what are the degrees of freedom for sample variance and what does this figure represent?

Accepted Answer

A) df = 24;it represents the number of scores that are free to vary in a sample. 
B) df = 23;it represents the number of scores that are free to vary in a sample. 
C) df = 23;dividing SS by df makes the sample variance a biased estimator of the population variance. 
D) df = 24;dividing SS by df makes the sample variance an unbiased estimator of the population variance.

Question 7

Which of the following is the best explanation for why the standard deviation is almost always reported with the mean?

Accepted Answer

A) The standard deviation measures the spread of scores from the mean,so it is important to know both the mean and the standard deviation. 
B) The standard deviation is also a measure of central tendency,so it is important to report this value with the mean. 
C) The mean and standard deviation estimate basically the same thing,so these values are typically reported together. 
D) This is not true;the standard deviation is rarely reported with the mean.

Question 8

The sample variance will be larger than the population variance for the following data: 3,5,4,7,3,5,4,8,and 9.

Accepted Answer

A) True 
 B)False

Question 9

A researcher measures the time (in seconds)it takes a sample of 26 participants to respond to a stimulus presented on a computer screen.The standard deviation for response times is 6.In this example,what is the value for SS?

Accepted Answer

A) 36 
B) 150 
C) 900 
D) There is not enough information to answer this question.

Question 10

Each deviation in the numerator for variance is squared because

Accepted Answer

A) without squaring each deviation,the solution for SS would be zero 
B) this inflates the value for variance,making it more accurate 
C) without squaring each deviation,the solution could be negative 
D) both A and C

Question 11

A researcher computes the computational formula for SS,as finds that ∑x = 39 and ∑x2 = 271.If this is a sample of 6 scores,then what would SS equal using the definitional formula?

Accepted Answer

A) 17.5 
B) 3.5 
C) 232 
D) not possible to know because the sample mean is not given

Question 12

Which of the following distributions has the largest variability?

Accepted Answer

A) scores: 1,3,6,9,and 12 
B) scores: 22,24,26,28,and 30 
C) scores: 2,3,4,5,and 6 
D) scores: 1,2,3,4,and 5

Question 13

The definitional formula for variance is stated in terms of how variance is defined.

Accepted Answer

A) True 
 B)False

Question 14

Multiplying or dividing each score using the same constant will not change the standard deviation.

Accepted Answer

A) True 
 B)False

Question 15

As a general rule,an interquartile range is a better estimate of variability than the IQR.

Accepted Answer

A) True 
 B)False

Question 16

All other things being equal,the value in the numerator is computed the same for sample variance and population variance.

Accepted Answer

A) True 
 B)False

Question 17

The standard deviation is always positive or equal to 0.

Accepted Answer

A) True 
 B)False

Question 18

The sample variance is computed by dividing SS by ____;whereas the population variance is computed by dividing SS by ____.

Accepted Answer

A) N;df 
B) df;n - 1 
C) df;N 
D) n - 1;df

Question 19

The standard deviation is typically reported in research reports with the mean for a data set.

Accepted Answer

A) True 
 B)False

Question 20

A researcher records the time in seconds it takes a sample of participants to walk alone through a dark portion of campus.The researcher computes SS = 1,200.Assuming that a sample of 25 participants was observed in this study,what is the standard deviation for these data?

Accepted Answer

A) 48 seconds 
B) 50 seconds 
C) 6.9 seconds 
D) 7.1 seconds

Exam 4: Summarizing Data: Variability

The 50th percentile is also called the median quartile.

One reason the denominator for sample variance is (n - 1)is because this makes it an unbiased estimator of the population variance.

Adding or subtracting the same constant to each score will not change the standard deviation.

For nonnormal distributions,99.7% of data will fall within three standard deviations of the mean.

A main disadvantage of computing a range is that it takes into consideration only two values regardless of the number of scores in a distribution.

A researcher selects a sample of 24 participants and has them complete a survey on dating preferences.In this example,what are the degrees of freedom for sample variance and what does this figure represent?

Which of the following is the best explanation for why the standard deviation is almost always reported with the mean?

The sample variance will be larger than the population variance for the following data: 3,5,4,7,3,5,4,8,and 9.

A researcher measures the time (in seconds) it takes a sample of 26 participants to respond to a stimulus presented on a computer screen.The standard deviation for response times is 6.In this example,what is the value for SS?

Each deviation in the numerator for variance is squared because

A researcher computes the computational formula for SS,as finds that ∑x = 39 and ∑x² = 271.If this is a sample of 6 scores,then what would SS equal using the definitional formula?

Which of the following distributions has the largest variability?

The definitional formula for variance is stated in terms of how variance is defined.

Multiplying or dividing each score using the same constant will not change the standard deviation.

As a general rule,an interquartile range is a better estimate of variability than the IQR.

All other things being equal,the value in the numerator is computed the same for sample variance and population variance.

The standard deviation is always positive or equal to 0.

The sample variance is computed by dividing SS by ;whereas the population variance is computed by dividing SS by .

The standard deviation is typically reported in research reports with the mean for a data set.

A researcher records the time in seconds it takes a sample of participants to walk alone through a dark portion of campus.The researcher computes SS = 1,200.Assuming that a sample of 25 participants was observed in this study,what is the standard deviation for these data?