Graphical Displays 1 M03- Graphical Displays 1 1  Department of ISM, University of Alabama, Graphical Displays of Data

Graphical Displays 1 M03- Graphical Displays 1 2  Department of ISM, University of Alabama, Lesson Objectives  Learn how to construct two graphs for a quantitative variable.  Learn why the “distribution” of a quantitative variable is informative.  Learn how to recognize and describe four characteristics of the distribution of a quantitative variable.

Graphical Displays 1 M03- Graphical Displays 1 3  Department of ISM, University of Alabama, Obtaining Data Files from Outlook Data files from me are in the following location: Public Folders All Public Folders Student Folders Class Related Folders Management Science and Statistics Faculty Dr. Mansfield ST 260 Click the desired posting to select it File –> Save Attachments… There may be more than one version (.txt,.xls).

Graphical Displays 1 M03- Graphical Displays 1 4  Department of ISM, University of Alabama, Graphs  Histogram  Stem-and-leaf plot for a single quantitative variable

Graphical Displays 1 M03- Graphical Displays 1 5  Department of ISM, University of Alabama, Handout: Data for 100 Households (FAM100) Income1Annual income of principal wage earner Income2Annual income of secondary wage earner FamSizeFamily size Own?Own or rent (1 = own, 0 = rent) TotalDebtTotal indebtedness (excluding mortgage) HousingMonthly house payment or rent UtilityAverage monthly utility expenditure CityCity of residence (1, 2, 3, 4) Fam100 data

Graphical Displays 1 M03- Graphical Displays 1 6  Department of ISM, University of Alabama, Histogram Income1 Frequency Fam100 data

Graphical Displays 1 M03- Graphical Displays 1 7  Department of ISM, University of Alabama, Additional Comments  Try using different class intervals; find the histogram that best describes the data distribution.  Always title your graphs and label the axes with meaningful variable names.  Cut-and-paste to paste Excel and Minitab graphs into Word documents for final reports.

Graphical Displays 1 M03- Graphical Displays 1 8  Department of ISM, University of Alabama, “Distribution” of a Quantitative Variable Gives an indication of how likely values is different segments of the range of the variable are of being observed.

Graphical Displays 1 M03- Graphical Displays 1 9  Department of ISM, University of Alabama, Stem-and-leaf plot of Income1 N = 100 Leaf Unit = (22) Fam100 data Stem-and-Leaf Plot

Graphical Displays 1 M03- Graphical Displays 1 10  Department of ISM, University of Alabama, Income1 Stems Leaves

Graphical Displays 1 M03- Graphical Displays 1 11  Department of ISM, University of Alabama, Income1 Stems Leaves Leaf Unit = 100

Graphical Displays 1 M03- Graphical Displays 1 12  Department of ISM, University of Alabama, Income1 Stems Leaves Leaf Unit = 10

Graphical Displays 1 M03- Graphical Displays 1 13  Department of ISM, University of Alabama, ’s ’s ’s ’s ’s 7 0-4’s Income1 Stems Leaves Leaf Unit = 1000 Split Stems

Graphical Displays 1 M03- Graphical Displays 1 14  Department of ISM, University of Alabama, Depth Gauge

Graphical Displays 1 M03- Graphical Displays 1 15  Department of ISM, University of Alabama, Stem-and-Leaf Notes  The “leaf” for a data value is always the first digit to the right of the dividing line.  The “stem” for a data value is all digits to the left of the dividing line.  The “leaf” is always one digit, but a “stem” can be more than one digit.

Graphical Displays 1 M03- Graphical Displays 1 16  Department of ISM, University of Alabama, “Distribution” of a Quantitative Variable  Illustrated by a histogram or a stem-and-leaf plot.  Indicates how likely values is different segments of the range of the variable are of being observed.

Graphical Displays 1 M03- Graphical Displays 1 17  Department of ISM, University of Alabama, Key Features of Data Distributions    

Graphical Displays 1 M03- Graphical Displays 1 18  Department of ISM, University of Alabama, Shapes of data distributions 

Graphical Displays 1 M03- Graphical Displays 1 19  Department of ISM, University of Alabama, Frequency _____________ Distribution

Graphical Displays 1 M03- Graphical Displays 1 20  Department of ISM, University of Alabama, Frequency ________________

Graphical Displays 1 M03- Graphical Displays 1 21  Department of ISM, University of Alabama, Frequency ______________

Graphical Displays 1 M03- Graphical Displays 1 22  Department of ISM, University of Alabama, Frequency _____________

Graphical Displays 1 M03- Graphical Displays 1 23  Department of ISM, University of Alabama, Typical Values:  Center of gravity  "Middle" value  Most frequently occurring value.

Graphical Displays 1 M03- Graphical Displays 1 24  Department of ISM, University of Alabama, Outliers: Extreme or unusual observations. Could be mistakes, but not necessarily.

Graphical Displays 1 M03- Graphical Displays 1 25  Department of ISM, University of Alabama, Frequency Growing Season (Days)

Graphical Displays 1 M03- Graphical Displays 1 26  Department of ISM, University of Alabama, Frequency Growing Season (Days)

Graphical Displays 1 M03- Graphical Displays 1 27  Department of ISM, University of Alabama, Frequency Growing Season (Days) Typical value? Typical value?

Graphical Displays 1 M03- Graphical Displays 1 28  Department of ISM, University of Alabama, Frequency Growing Season (Days) Typical value? Typical value? Mean = _________

Graphical Displays 1 M03- Graphical Displays 1 29  Department of ISM, University of Alabama, Frequency Growing Season (Days) Typical value? Typical value? median = ________

Graphical Displays 1 M03- Graphical Displays 1 30  Department of ISM, University of Alabama, Frequency Growing Season (Days) Outliers ? Outliers ?

Stemplots: “Number of miles put on a sample of rent cars in April”. X = Mileage. Stem X100 Leaf

Stemplots: “Number of miles put on a sample of rent cars in April”. X = Mileage. Stem X100 Leaf n = Max = Median = Min =