1 / 20

Histograms

Mathematics for Business Decisions, part I. Histograms. Math 115a. Math 115a. Histograms.

albert
Télécharger la présentation

Histograms

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Mathematics for Business Decisions, part I Histograms Math 115a Math 115a

  2. Histograms Histograms • A histogram is a table/graph that sorts data into pre-specified categories, or bins. Math 115a

  3. Histograms Histograms, Excel 2003 • You can find Histograms in Excel 2003 under: • Tools • Data Analysis • Histograms • If you don’t see “Data Analysis” under Tools: • Go to Add Ins… under Tools • Select both Analysis Toolpak and Analysis Toolpak-VBA (you may need your original installation disc) Math 115a

  4. Histograms Histograms, Excel 2007 • You can find Histograms in Excel 2007 under: • Data tab • Analysis group, Data Analysis • Histograms • If you don’t see the Analysis groupin the Data tab: • Go to Add Ins… in Excel Options under the Office button • Select both Analysis Toolpak and Analysis Toolpak-VBA (you may need your original installation disc) Math 115a

  5. Histograms Histogram • You’ll need to specify: • Input Range • Bin Range • Labels (if applicable) • Output Range Math 115a

  6. Histograms Histogram window • Input Range: • This is the range of cells that contains the data you want to sort. • Enter this as a typical cell range in Excel: A2:A101, e.g. Math 115a

  7. Histograms Histogram Window • Bin Range: • The range of cells that contain your pre-specified bin ranges (i.e. your categories). • Enter this as a typical cell range in Excel: H2:H10, e.g. Math 115a

  8. Histograms Bins in Excel • Again, “bins” are your categories that you want to sort your data into. • You must specify the intervals that you want, or else you’ll get some odd endpoints! • Let’s say you want to sort the test scores into the categories 40-49, 50-59, 60-69, … , 90-99. • You will designate these intervals by the right endpoint for each interval: 49, 59, 69, …, 99 Math 115a

  9. Histograms Bins in Excel • Excel will read it as the following: Math 115a

  10. Histograms Histogram Window • Labels • You MUST be consistent: • Check the box: ONLY if you included the column headers for both the input and bins. • Leave unchecked: ONLY if your ranges contained only the data, and no headers. Math 115a

  11. Histograms Histogram Window • Output Range • Input only the cell in which you want the output to START. You should have several clear columns to the right of this cell, and several empty cells below this. • NOTE: By default, “New Worksheet Ply:” is selected. When you choose “Output Range” it will automatically highlight the “Input Range” space. BE CAREFUL! You click in the box by “Output Range” before selecting a cell. Math 115a

  12. Histograms Output • The output from Excel repeats your bin limits, and also gives the frequency count. • “More” should be zero. If not, your bin limits did not go high enough to accommodate your data. Math 115a

  13. Histograms Choosing appropriate bin limits • Bins do not need to start at zero! • Find the range of your data • range = maximum – minimum • Your first bin limit should be reasonably above your minimum data point • Good rule-of-thumb: your first bin limit should be equal to your minimum value + bin width • Your last bin limit should be greater than your maximum data point Math 115a

  14. Histograms Choosing the bin size • Rule of thumb: start your bin size by the calculation: range of data  10 • Make your endpoints nice numbers, but make sure every bin has the same size interval • See how your histogram looks: • If it’s too “blocky”, increase the number of bins by decreasing the bin size • If it’s too detailed, decrease the number of bins by increasing the bin size Math 115a

  15. Histograms Graphing the histogram • Histograms are typically shown as a column graph. • Use Excel’s Chart Wizard • Select Column Graph as the type • In “Data Range” select only the non-More Frequency cells. • Click on the “Series” tab and enter the range of cells for labels for “X-axis labels” Math 115a

  16. Histograms Graphing window: Data Math 115a

  17. Histograms Graphing window: Series Math 115a

  18. Histograms Labels • NOTE: Labels will always be centered under each column. Therefore it is not a good idea to label a column by its right endpoint. Labeling by the full interval (i.e. “40-49”) is acceptable only if you have enough room, and not too many bins. Usually it is best to have a column of midpoints for each interval, and label with these. (Remember, the label is centered under each column!) Math 115a

  19. Histograms Spacing • We know grades can range from 0-100. Therefore, it makes sense to demonstrate this continuum of grades by no space between columns: Math 115a

  20. Histograms Spacing • Right-click on any column • Select “Format Data Series” • Select the “Options” tab • Set “Gap width” to zero Math 115a

More Related