WGU CHapter Descriptive stats for a single variable

You sample the ages for each of 100 people from the following 4 populations. Which would you assume would have the greatest standard deviation?

People at an amusement park

When analyzing a box-and-whisker plot, what proportion of the data lies between the max and min values?

100% The proportion of the data lies between the max and min values represents all of the data.

Using the following box-and-whisker plot below, estimate the value of Q1.

11.5 In a box plot, the value of Q1 is equal to the left edge of the rectangle in the box plot. In this box plot, the left edge of the rectangle is approximately 11.5.

Use the box-and-whisker plot below to answer the following question. Determine the mean number of days a product stays in inventory.

13 This mean of this data set cannot be determined from the box plot. To calculate the mean you would need to sum all of the data values in the data set and divide that sum by the number of data points in the set.

A normally distributed data set has a mean value of 85 and standard deviation 20 The data point values that fall between one and two standard deviations below the mean will range from __________ to _____________ ?

45 to 65 We know that the standard deviation is 20 so two standard deviations is equal to 40 (20×2=40). Therefore, a data value that is two standard deviations below the mean is 85−40 is equal to 45. To obtain the second value subtract one standard deviation, 20, from the mean: 85−20=65 Therefore, the data point values that will fall within 1 and 2 standard deviations below the mean will range from 45 to 65

Assuming that the heights of adult males in the United States are normally distributed, what is the approximate percentage of adult males who have a height (in ft.) within 1 standard deviation of the mean?

68% The Standard Deviation Rule says that 68% of the values will fall within 1 standard deviation of the mean.

A data point that is significantly distant from the other data points in the data set is called:

An outlier An outlier is a data point that is significantly distant from other data points in the data set.

Which of the following best describes a measure of spread?

Range of pages for volumes in an Encyclopedia complete volume set. Range is one example of a measure of spread.

About 95 percent of results in a normal distribution fall between one standard deviation below the mean and one standard deviation above the mean. True or False?

False According to The Empirical Rule, approximately 68% of the data points in a dataset will be within 1 standard deviation of the mean. 95% of all values are within 2 standard deviations of the mean.

Which of the following would be the best option to graphically display continuous data?

Histogram A histogram is a graph that displays continuous data. Histograms measure how continuous data is distributed over various ranges.

You are asked to produce a graph to display waiting times for students visiting the computer help desk collected over the past academic year. What is the BEST type of graph to use?

Histogram The data is both continuous and quantitative. This data set can also be assumed to be a large data set as the waiting times were collected over an entire academic year. Therefore, the best way to display a large quantitative data set is a histogram.

You survey CEOs in the Boston area to determine the number of years of post-secondary education they have. What type of graph would be BEST to use to display the distribution of this data?

Histogram This is quantitative data, so the choice is between C and D, but a histogram is best used to illustrate the distribution of a large set of quantitative data.

Of the 3 measures of central tendency, which one is MOST affected by outliers?

Mean

how are the mean and median of a sample related if the distribution is skewed to the right?

Mean is greater than median. If the distribution is skewed to the right, the mean is greater than median.

How are the mode and mean of a sample related if the distribution is positively skewed?

The mode is less than the mean. The mode is less than the mean, as the mean moves towards the skew.

Which of the following will result in a data set with more than one value?

The number of years for each employee in upper management represented in this sample would represent a range of values. The other 3 answers are single measured values.

Which of the following best describes a measure of spread?

The salary range of analysts in each department of an international financial firm.

How are the mean, median, and mode of a sample related if the distribution is normally distributed?

The values are all equal In a normal distribution data is symmetrical, so the mean, median, and mode are all equal.

A set of data is normally distributed with a mean of 85 and standard deviation 20. The data point values that fall within one standard deviation range from ___________ to ___________?

low is 65 high is 105 80-20=65 80+20=105

Which of the following would be the best option to graphically display continuous data?

quantitative data Quantitative data consists of data values that are numbers, representing quantities that can be counted or measured.