Exam 4: Numerical Descriptive Techniques

Hours of Playing Video Games Suppose that the following data provide the hours of playing video games per week for a sample of 15 high school students in Roanoke, Virginia: 5, 11, 25, 19, 18, 20, 27, 13, 8, 10, 15, 19, 18, 9, and 12. -{Hours of Playing Video Games Narrative} Determine the location and value of the first quartile.

The distance between the 25th percentile and the median is always the same as the distance between the median and the 75th percentile.

The 10th ____________________ is the value for which 10% of the observations are less than that value.

The range is considered the weakest measure of variability.

The ____________________ is the least effective of all the measures of variability.

If the coefficient of correlation r = 0, then there can be no relationship whatsoever between the dependent variable y and the independent variable x.

____________________ are extremely large or extremely small observations.

Ages of Jockeys The following data represent the ages in years of a sample of 25 jockeys from a local race track: 31, 43, 56, 23, 49, 42, 33, 61, 44, 28, 48, 38, 44, 35, 40, 64, 52, 42, 47, 39, 53, 27, 36, 35, and 20. -{Ages of Jockeys Narrative} Construct a relative frequency distribution for the data, using five class intervals and the value 20 as the lower limit of the first class.

The Empirical Rule states that the approximate percentage of measurements in a data set (providing that the data set has a bell shaped distribution) that fall within two standard deviations of their mean is approximately:

Hours Worked per Week The following data represent the hours worked per week 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, and 20. -{Hours Worked per Week Narrative} Compare the mean and median hours for these employees and use them to discuss the shape of the distribution.

The coefficient of variation is a measure of variability.

What statistics and graphs can you use to answer the following question: Is the distribution symmetric? If not, is it skewed? If symmetric, is it bell shaped?

In a positively skewed distribution, the percentage of data between the smallest observation and Q₁ is less than the percentage of data between Q₃ and the largest observation.

Hours Worked per Week The following data represent the hours worked per week 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, and 20. -{Hours Worked per Week Narrative} Construct a stem and leaf display for the hours.

Computers The following data represent the number of computers owned by a sample of 10 families from Chicago: 4, 2, 1, 1, 5, 3, 0, 1, 0, and 2. -{Computers Narrative} Is the distribution of the number of computers symmetric or skewed? Why?

In a histogram, the proportion of the total area which must be to the left of the median is:

Which of the following statements is true?

Longevity and Salary A sample of eight observations of variables x (years of experience) and y (salary in $1,000s) is shown below: -{Longevity and Salary Narrative} Determine the least squares line, and use it to estimate the value of y for x = 6.

Ages of Retirees A sociologist recently conducted a survey of retirees over 65 years of age whose net worth is too high to qualify for Medicaid and who have no private health insurance.The ages of 20 uninsured retirees were as follows: 65, 66, 67, 68, 69, 70, 71, 73, 74, 75, 78, 79, 80, 81, 86, 87, 91, 92, 94, and 97. -{Ages of Retirees Narrative} Calculate the third quartile of the ages of the uninsured retirees.

The ____________________ is calculated by finding the middle of the data set, when the data are ordered from smallest to largest.