Hi everyone! Read through the material below, watch the videos, work on the Excel lecture and follow up with your instructor if you have questions.
Learning Outcomes.
- Collect, organize and graph raw data.
- Know the difference between numerical and categorical variables.
- Create grouped frequency distributions and histograms. Class intervals should be of equal width, chosen to effectively reveal informative patterns in the data, between 5 (for overview) and 15 (for some detail).
- Describe a graphical display by first describing the overall pattern (e.g., roughly symmetrical or skewed right or left) and then deviations from that pattern, such as outliers.
- Understand that the vertical axis of the histogram may be scaled for frequency or percentage (proportion), but the choice of vertical scaling will not affect the important features revealed by a histogram.
- Excel: know how to freeze panes, sort and filter data, format tables, make charts and use pivot tables.
Topic. This lesson covers: Graphical Descriptive Techniques
- Openstax Introductory Statistics:
- Introductory Statistics by Sheldon Ross, 3rd edition: Sections 2.1-2.4
- Statistics with Microsoft Excel by Beverly J. Dretzke, 5th edition: SORT, FREQUENCY, P. 28 – 29
WeBWorK: Sets 1.3, 2.1 & 2.2
Finish the mini course by GCFglobal (lessons 17-34). When doing this course, have an Excel file open (perhaps the provided practice workbook).
Below you will find videos to help you organize and display data in Excel. By 2016, Microsoft had added a histogram to its charts. By clicking on the bottom axis, you can specify the number of bins or the class width. A further option is to use the data array calculation “frequency”. Here is a step-by-step guide. Once you have the table, you can create appropriate labels using columns of the left and right boundaries for each interval and the “concatenate” function.
Videos
While Excel does not have something builtin for stem and leaf plots, there are macros available.
- One suggestion for improvement in the above video: select all the columns whose width needs adjusting and adjust their width all at once or set it to a fixed number. This is important as the widths of the columns where the leaves are should be uniform.
- Think of ways to use formulas to do some of the processing such as how to extract the 10’s digit, etc. You can also use paste special for instance to move data from a row into a column or vice versa. The challenge is to do everything without typing any numbers; retying of data is discouraged as it can result in copying errors.
The applied view
Watch the video Stemplots.
- List some of the variables that were taken on soldiers for the sizing data bank.
- What was the overall shape of the distribution of soldiers’ foot lengths?
- About where was the center of the distribution?
- What variable was used to measure fuel economy on Toyota’s line of vehicles?
- Focus on the stemplot of fuel economy for Toyota’s 2012 line. What new information became evident (or more clear) when the stem was expanded?
- What was learned from back-to-back stemplots about the change in fuel economy in Toyota’s vehicle line from 1984 to 2012?
Watch the video Histograms.
- The video opens by describing a study of lightning strikes in Colorado. What variable does the first histogram display?
- In this lightning histogram, what does the horizontal scale represent? What does the vertical scale represent?
- Was the overall shape of this histogram symmetric, skewed, or neither?
- Why were a few values in the second lightning histogram called outliers?
- When you choose the classes for a histogram, what property must the classes have if the histogram is to be correct?
- What happens to a histogram if you use too many classes? What happens if you use too few?
Exit Ticket
What type of data would you use a histogram to display? Can you think of an example of data you might encounter in your everyday life which could be displayed in a histogram?
