Exam 4: Numerical Descriptive Techniques

The ____________________ of a linear relationship is hard to interpret from the covariance, but it is easy to interpret from the correlation.

If the standard deviation of x is 18, the covariance of x and y is 120, the coefficient r = 0.90, then the standard deviation of y is 54.87.

Which of the following statements about the mean is not always correct?

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} Compute the mean number of computers.

Yearly Donations The following data represent the yearly donations (in thousands of dollars) of a sample of 13 benefactors: 26.5, 23.5, 29.7, 24.8, 21.1, 24.3, 20.4, 22.7, 27.2, 23.7, 24.1, 24.8, and 28.2. -{Yearly Donations Narrative} a. Describe the shape of distribution of donations based on the values of the quartiles. b. Give a possible reason for the shape of this data set, in terms of donations.

A population with 200 elements has a variance of 20.From this information, it can be shown that the population standard deviation is 10.

The coefficient of variation allows us to compare two sets of data based on different measurement units.

Strip Mall Rent Monthly rent data in dollars for a sample of 10 stores in a small town in South Dakota are as follows: 220, 216, 220, 205, 210, 240, 195, 235, 204, and 250. -{Strip Mall Rent Narrative} Compute the sample monthly average rent.

The ____________________ is not as sensitive to extreme values as the ____________________.

The ____________________ is the least desirable of all the measures of central location.

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} Find the modal hours.

A sample of 12 construction workers has a mean age of 25 years.Suppose that the sample is enlarged to 14 construction workers, by including two additional workers having common age of 25 each.Find the mean of the sample of 14 workers.

In a perfectly symmetric distribution, which of the following statements is false?

Salaries of Employees The following data represent the yearly salaries (in thousands of dollars) of a sample of 13 employees of a firm: 26.5, 23.5, 29.7, 24.8, 21.1, 24.3, 20.4, 22.7, 27.2, 23.7, 24.1, 24.8, and 28.2. -{Salaries of Employees Narrative} Compute the mean salary.

Ages of Volunteers The following data represent the ages in years of a sample of 25 volunteers from a charitable organization: 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 Volunteers Narrative} Compute the range of the data and express the number in the appropriate unit.

According to Chebysheff's Theorem, at least 93.75% of observations should fall within 4 standard deviations of the mean.

Salaries of Employees The following data represent the yearly salaries (in thousands of dollars) of a sample of 13 employees of a firm: 26.5, 23.5, 29.7, 24.8, 21.1, 24.3, 20.4, 22.7, 27.2, 23.7, 24.1, 24.8, and 28.2. -{Salaries of Employees Narrative} Compare the mean salary with the median salary and use them to describe the shape of the distribution.

The value of the mean times the number of observations equals the sum of the observations.

In a histogram, the proportion of the total area which must be to the right of the mean is:

According to the Empirical Rule, if the data form a bell shaped normal distribution approximately ____________________ percent of the observations will be contained within 3 standard deviations around the mean.