ISYS 5503: CH 3

The variance of the sample a. can never be negative b. can be negative c. cannot be zero d. cannot be less than one

a. can never be negative

In computing descriptive statistics from grouped data, a. data values are treated as if they occur at the midpoint of a class b. the grouped data result is more accurate than the ungrouped result c. the grouped data computations are used only when a population is being analyzed d. None of these alternatives is correct.

a. data values are treated as if they occur at the midpoint of a class

When data are positively skewed, the mean will usually be a. greater than the median b. smaller than the median c. equal to the median d. positive

a. greater than the median

The variance of a sample of 81 observations equals 64. The standard deviation of the sample equals a. 9 b. 4096 c. 8 d. 6561

c. 8

Which of the following symbols represents the size of the sample a. σ2 b. σ c. N d. n

d. n

The difference between the largest and the smallest data values is the a. variance b. interquartile range c. range d. coefficient of variation

c. range

A numerical value used as a summary measure for a sample, such as sample mean, is known as a a. population parameter b. sample parameter c. sample statistic d. population mean

c. sample statistic

The measure of dispersion that is influenced most by extreme values is a. the variance b. the standard deviation c. the range d. the interquartile range

c. the range

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

c. the range is influenced too much by extreme values

The symbol σ is used to represent a. the variance of the population b. the standard deviation of the sample c. the standard deviation of the population d. the variance of the sample

c. the standard deviation of the population

When the smallest and largest percentage of items are removed from a data set and the mean is computed, the mean of the remaining data is a. the median b. the mode c. the trimmed mean d. any of the above

c. the trimmed mean

The 75th percentile is referred to as the a. first quartile b. second quartile c. third quartile d. fourth quartile

c. third quartile

Which of the following is not a measure of central location? a. mean b. median c. variance d. mode

c. variance

The symbol σ2 is used to represent a. the variance of the population b. the standard deviation of the sample c. the standard deviation of the population d. the variance of the sample

a. the variance of the population

The measure of dispersion which is not measured in the same units as the original data is the a. median b. standard deviation c. coefficient of determination d. variance

d. variance

The median of a sample will always equal the a. mode b. mean c. 50th percentile d. all of the above answers are correct

c. 50th percentile

The pth percentile is a value such that at least p percent of the observations are a. less than or equal to this value b. less than this value c. more than or equal to this value d. more than this value

a. less than or equal to this value

The most important statistical descriptive measure of the location of a data set is the a. mean b. median c. mode d. variance

a. mean

In computing the mean of a sample, the value of ∑xi is divided by a. n b. n - 1 c. n + 1 d. n - 2

a. n

μ is an example of a a. population parameter b. sample statistic c. population variance d. mode

a. population parameter

If the variance of a data set is correctly computed with the formula using n - 1 in the denominator, which of the following is true? a. the data set is a sample b. the data set is a population c. the data set could be either a sample or a population d. the data set is from a census

a. the data set is a sample

The coefficient of correlation ranges between a. 0 and 1 b. -1 and +1 c. minus infinity and plus infinity d. 1 and 100

b. -1 and +1

The weights (in pounds) of a sample of 36 individuals were recorded and the following statistics were calculated. mean = 160 range = 60 mode = 165 variance = 324 median = 170 The coefficient of variation equals a. 0.1125% b. 11.25% c. 203.12% d. 0.20312%

b. 11.25%

The variance of a sample of 169 observations equals 576. The standard deviation of the sample equals a. 13 b. 24 c. 576 d. 28,461

b. 24

The hourly wages of a sample of 130 system analysts are given below. mean = 60 range = 20 mode = 73 variance = 324 median = 74 The coefficient of variation equals a. 0.30% b. 30% c. 5.4% d. 54%

b. 30%

A numerical measure of linear association between two variables is the a. variance b. covariance c. standard deviation d. coefficient of variation

b. covariance

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

b. is the same as the 25th percentile

Which of the following provides a measure of central location for the data? a. standard deviation b. mean c. variance d. range

b. mean

The 50th percentile is the a. mode b. median c. mean d. third quartile

b. median

The value which has half of the observations above it and half the observations below it is called the a. range b. median c. mean d. mode

b. median

The most frequently occurring value of a data set is called the a. range b. mode c. mean d. median

b. mode

When should measures of location and dispersion be computed from grouped data rather than from individual data values? a. as much as possible since computations are easier b. only when individual data values are unavailable c. whenever computer packages for descriptive statistics are unavailable d. only when the data are from a population

b. only when individual data values are unavailable

Which of the following is not a measure of dispersion? a. the range b. the 50th percentile c. the standard deviation d. the interquartile range

b. the 50th percentile

The coefficient of variation is a. the same as the variance b. the standard deviation divided by the mean times 100 c. the square of the standard deviation d. the mean divided by the standard deviation

b. the standard deviation divided by the mean times 100

Since the population size is always larger than the sample size, then the sample statistic a. can never be larger than the population parameter b. can never be equal to the population parameter c. can be smaller, larger, or equal to the population parameter d. can never be smaller than the population parameter

c. can be smaller, larger, or equal to the population parameter

The coefficient of correlation a. is the same as the coefficient of determination b. can be larger than 1 c. cannot be larger than 1 d. cannot be negative

c. cannot be larger than 1

The median is a measure of a. relative dispersion b. absolute dispersion c. central location d. relative location

c. central location

A numerical measure of linear association between two variables is the a. variance b. coefficient of variation c. correlation coefficient d. standard deviation

c. correlation coefficient

The sample variance a. is always smaller than the true value of the population variance b. is always larger than the true value of the population variance c. could be smaller, equal to, or larger than the true value of the population variance d. can never be zero

c. could be smaller, equal to, or larger than the true value of the population variance

Which of the following is a measure of dispersion? a. percentiles b. quartiles c. interquartile range d. all of the above are measures of dispersion

c. interquartile range

The numerical value of the standard deviation can never be a. larger than the variance b. zero c. negative d. smaller than the variance

c. negative

The variance can never be a. zero b. larger than the standard deviation c. negative d. smaller than the standard deviation

c. negative

When the data are skewed to the right, the measure of Skewness will be a. negative b. zero c. positive d. one

c. positive

The standard deviation of a sample of 100 observations equals 64. The variance of the sample equals a. 8 b. 10 c. 6400 d. 4,096

d. 4,096

The heights (in inches) of 25 individuals were recorded and the following statistics were calculated mean = 70 range = 20 mode = 73 variance = 784 median = 74 The coefficient of variation equals a. 11.2% b. 1120% c. 0.4% d. 40%

d. 40%

Which of the following symbols represents the size of the population? a. σ2 b. σ c. μ d. N

d. N

If two groups of numbers have the same mean, then a. their standard deviations must also be equal b. their medians must also be equal c. their modes must also be equal d. None of these alternatives is correct.

d. None of these alternatives is correct.

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

d. None of these alternatives is correct.

The sum of deviations of the individual data elements from their mean is a. always greater than zero b. always less than zero c. sometimes greater than and sometimes less than zero, depending on the data elements d. always equal to zero

d. always equal to zero

When computing the mean of a set of values xi, the value of ∑xi a. can never be zero b. can never be negative c. must always be positive d. can be any value

d. can be any value

When computing the mean, the smallest value a. can never be negative b. can never be zero c. can never be less than the mean d. can be any value

d. can be any value

The numerical value of the variance a. is always larger than the numerical value of the standard deviation b. is always smaller than the numerical value of the standard deviation c. is negative if the mean is negative d. can be larger or smaller than the numerical value of the standard deviation

d. can be larger or smaller than the numerical value of the standard deviation

The descriptive measure of dispersion that is based on the concept of a deviation about the mean is a. the range b. the interquartile range c. the absolute value of the range d. the standard deviation

d. the standard deviation

Since the population is always larger than the sample, the value of the sample mean a. is always smaller than the true value of the population mean b. is always larger than the true value of the population mean c. is always equal to the true value of the population mean d. could be larger, equal to, or smaller than the true value of the population mean

d. could be larger, equal to, or smaller than the true value of the population mean

The mean of a sample a. is always equal to the mean of the population b. is always smaller than the mean of the population c. is computed by summing the data values and dividing the sum by (n - 1) d. is computed by summing all the data values and dividing the sum by the number of items

d. is computed by summing all the data values and dividing the sum by the number of items

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

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

The measure of location which is the most likely to be influenced by extreme values in the data set is the a. range b. median c. mode d. mean

d. mean

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

d. positive relation between the independent and the dependent variables

If index i (which is used to determine the location of the pth percentile) is not an integer, its value should be a. squared b. divided by (n - 1) c. rounded down d. rounded up

d. rounded up

The interquartile range is a. the 50th percentile b. another name for the variance c. the difference between the largest and smallest values d. the difference between the third quartile and the first quartile

d. the difference between the third quartile and the first quartile