Exam 5: Numerical Descriptive Measures

Which of the following statements best describes the mean of a data set?

The average score for a class of 30 students was 75. The 20 male students in the class averaged 70. The female students in the class averaged:

When approximating descriptive measures for grouped data, the shape of the distribution within each class is ignored.

a. Calculate the covariance and the coefficient of correlation for the following sample. x 9 6 7 5 8 y 19 14 16 12 15 b. What do these statistics tell you about the relationship between X and Y?

The following data represent the ages (in years) of a sample of 25 employees from a government department: 31 43 56 23 49 42 33 61 44 28 48 38 44 35 40 64 52 42 47 39 53 27 36 35 20 The frequency distribution for the data, using five class intervals and the value 20 as the lower limit of the first class is given below. Class Limits Frequency 20 up to 30 4 30 up to 40 7 40 up to 50 9 50 up to 60 3 60 up to 70 2 Total 25 Find the mean of the grouped data.

A sample of 16 observations has a standard deviation of 2. Which of the following is the sum of the squared deviations from the sample mean?

The following data represent the ages (in years) of a sample of 25 employees from a government department: 31 43 56 23 49 42 33 61 44 28 48 38 44 35 40 64 52 42 47 39 53 27 36 35 20 Calculate the 1st quintile. (Hint: 1st quintile is L20)

Which of the following summary measures is affected by extreme values?

In a positively skewed distribution, the mean is larger than the median and the median is larger than the mode.

The following data represent the numbers of bedrooms in a sample of 10 suburban houses in Mel-bourne: 3 3 2 2 4 5 2 5 4 2 Use these data to answer the following question/s. -a. Compute the mean. b. Compute the median.

A basketball player has the following points for seven games: 20, 25, 32, 18, 19, 22, 30. Compute the following measures of central location and variability: a. mean. b. median. c. standard deviation. d. coefficient of variation.

When the distribution is skewed, the interquartile range is a better measure of variability than the standard deviation.

Quartiles divide the values in a data set into four parts of equal size.

Which measure of variability is appropriate when a sample is likely to contain one or several extreme values?

The following data provide the hours of television viewing per week for a sample of 15 high school students in Darwin: 5 11 25 19 18 20 27 13 8 10 15 19 8 9 12 a. Determine the locations and values of the first, second and third quartiles. b. Calculate the interquartile range. c. Interpret the value of the interquartile range.

The following data are the heights (in cm) of the 25 students in a business statistics class: 164 148 137 157 173 156 177 172 169 165 145 168 163 162 174 152 156 168 154 151 174 146 134 140 171 a. Compute the range of the data. b. Compute the range approximation to the standard deviation of the data. (Hint: S  Range/4.)

Which of the following statements is true?

Data from three samples are shown below: Sample A: 17 22 20 18 23 Sample B: 30 28 35 40 25 Sample C: 44 39 54 21 52 Examine the three samples. Without performing any calculations, indicate which sample has the greatest amount of variability and which sample has the least amount of variability.

If the coefficient of correlation r = +1, then the best-fit linear equation will actually be satisfied by all of the data points.

Lily has been keeping track of what she spends on eating out. The last week's expenditures for meals eaten out were $5.69, $5.95, $6.19, $10.91, $7.49, $14.53 and $7.66. The mean amount Lily spends on meals is $8.35.