Chapter 3 quiz

If the data distribution is symmetric, the skewness is _____. a. .5 b. 1 c. 0 d. None of these answers are correct.

c. 0

The standard deviation of a sample of 100 observations is 64. The variance of the sample is which of the following? a. 6,400 b. 8 c. 4,096 d. 10

c. 4,096

A researcher has collected the following sample data. 5 12 6 8 5 6 7 5 12 4 The 75th percentile is _____. a. 8 b. 7 c. 6 d. 5

a. 8

The measure of variability easiest to compute, but seldom used as the only measure, is the _____. a. range b. interquartile range c. standard deviation d. variance

a. range

The symbol for _____ is r. a. sample correlation b. sample covariance c. population covariance d. population correlation

a. sample correlation

A researcher has collected the following sample data. The mean of the sample is 5. 3 5 12 3 2 The coefficient of variation is _____. a. 264% b. 81.24% c. 330% d. 72.66%

b. 81.24%

The interquartile range is used as a measure of variability to overcome what difficulty of the range? a. The range is difficult to compute. b. The range is influenced too much by extreme values. c. The sum of the range variances is zero. d. The range is negative.

b. The range is influenced too much by extreme values.

If r = 0.48 for data set A and r = −0.48 for data set B, which of the following is true? a. The data values in A are all positive, while the data values in B are all negative. b. The two data sets have the same level of correlation. c. The variables in A are more strongly correlated than the variables in B. d. None of these answers are correct.

b. The two data sets have the same level of correlation.

If a data set has an even number of observations, the median _____. a. must be equal to the mean b. is the average value of the two middle items when all items are arranged in ascending order c. cannot be determined d. is the observation recorded most often

b. is the average value of the two middle items when all items are arranged in ascending order

The numerical value of the standard deviation can never be _____. a. larger than the variance b. negative c. zero d. All of these answers are correct.

b. negative

The 75th percentile is also the _____. a. second quartile b. third quartile c. fourth quartile d. first quartile

b. third quartile

The variance is equal to the _____. a. square root of the standard deviation b. inverse value of the standard deviation c. squared value of the standard deviation d. absolute value of the standard deviation

c. squared value of the standard deviation

Which of the following values of r indicates the strongest correlation? a. 0 b. .361 c. −.9 d. .82

c. −.9

The following is the frequency distribution for the speeds of a sample of automobiles traveling on an interstate highway. Speed (mph). Frequency 50−54 2 55−59 4 60−64 5 65−69 10 70−74 9 75−79 5 35 The standard deviation is _____. a. 6.969 b. 48.570 c. 50.000 d. 7.071

d. 7.071

Since the mode is the most frequently occurring data value, it _____. a. is always larger than the median b. can never be larger than the mean c. is always larger than the mean d. None of these answers are correct.

d. None of these answers are correct.

The coefficient of variation is _____. a. the same as the variance b. the square root of the variance c. the square of the standard deviation d. None of these answers are correct.

d. None of these answers are correct.

The mean of the sample _____. a. is always larger than the mean of the population from which the sample was taken b. can never be zero c. is always smaller than the mean of the population from which the sample was taken d. None of these answers are correct.

d. None of these answers are correct.

_____ can be used to determine the percentage of data values that must be within one, two, and three standard deviations of the mean for data having a bell-shaped distribution. a. Chebyshev's theorem b. A five-number summary c. A box plot d. The empirical rule

d. The empirical rule

Positive values of covariance indicate _____. a. the standard deviation is positive b. a positive variance of the x values c. a positive variance of the y values d. a positive relation between the x and y variables

d. a positive relation between the x and y variables

A graphical summary of data that is based on a five-number summary is a _____. a. scatter diagram b. histogram c. stem-and-leaf display d. box plot

d. box plot

In computing descriptive statistics for grouped data, the _____ are used to approximate the data values in each class. a. class lower limits b. class ranges c. class upper limits d. class midpoints

d. class midpoints

When the data are positively skewed, the mean will usually be _____. a. less than the median b. less than the mode c. greater than the mode d. greater than the median

d. greater than the median

A graph with skewness −1.8 would be which of the following? a. moderately skewed right b. highly skewed right c. moderately skewed left d. highly skewed left

d. highly skewed left

The first quartile _____. a. is the same as the 50th percentile b. is the same as the 75th percentile c. contains at least one third of the data elements d. is the same as the 25th percentile

d. is the same as the 25th percentile

A numerical measure, such as a mean, computed from a population is known as a _____. a. sample statistic b. sample parameter c. population statistic d. population parameter

d. population parameter