…LAB 1

DESCRIBING DATA GRAPHICALLY

NAME______LAB TIME______LAB BLDG______

  1. Go the the Stat301T webpage, click on Lab Instructions, Questions and Data. Then open the instructions and questions file. Then click on the Lab1 data file and save it to your own directory. Then open the Lab1 data file from your own directory.
  1. Scroll up to line 1 of the data file. Column A shows exam1 scores for Spring 04, and column B shows exam 3 scores.
  1. Make histograms for column A and column B. (DataData AnalysisHistogram). You must usually install the Data Analysis tools before you can use them. To install them, choose OfficeExcel Options. When Excel displays the Excel Options dialog box, select the Add-Ins item from the left box that appears along the left edge of the dialog box. Excel next displays a list of thepossible add-ins — including the Analysis ToolPak add-in. Select the Analysis ToolPak item and click Go. Excel displays the Add-Ins dialog box. SelectAnalysis ToolPak from this dialog box and click OK. Excel installs the Analysis ToolPak add-in. Then go back and do: DataData AnalysisHistogram.

On the histogram window, fill in the input range,(A2:A228), leave bin range blank, click on output range, fill in the output range, (C2), click on chart output and click OK. Close up the bars as follows: do a right click on any blue bar, click on Format Data Series, change Gap Width to No Gap. Repeat for Column B Histogram: input range (B2:B216), output range (C22).

  1. Describe both histograms with respect to shape, center, spread and outliers.

descriptor / Exam 1 (column A) / Exam 3 (column B)
Shape: left skewed, (long tail on lower end), right skewed (long tail on higher end )or symmetric, (lower tail and upper tail are similar and approx symmetric about center.
Center Value : Just choose a value which seems to be in the middle of the data values on the horizontal axis.
Spread: Fill in the minimum and the maximum after you get the descriptive statistics in Step 5. / minimum______
maximum______/ minimum______
maximum______
Outliers, yes or no? Outliers are values which look like they do not belong. If “yes”, determine their values by looking at the data which is in ascending order.
  1. Calculate descriptive statistics for column A and column B. (tools>data analysis>descriptive statistics) .
  1. Fill in input range, (a2:a228) and output range, C40, for Column A and (b2:b216) and F40 for Column B, click on summary statistics, click on OK
  1. Since the descriptive statistics do not include the 1st and 3rd quartiles, calculate these descriptors for column A and B using the following steps:

1)Go to C57 and type 1st Quartile. Then go to D57 and type =.

2)Go up to the tool bar, select quartile function,(The first time you try this you will probably have to click on select a category, choose Statistical and scroll down to get the QUARTILE function. After you use it once, it will stay on the recently used list on the toolbar.) and fill in the input range, a2:a228, in “array” box. Fill in 1 for 1st quartile, and click OK.

3)Go to C58 and type 3rd Quartile. Then go to D58 and type =. Go up to the tool bar, select quartile function, fill in the input range a2:a228. Fill in 3 for the 3rd quartile, click OK.

4)Repeat steps 1-3 for quartiles for column B. Put them in F57 and F58.

  1. For SYMMETRIC data patterns we like to describe the data with two numbers, the MEAN (for the center value) and the STANDARD DEVIATION (for the spread going away from center).
  1. For LEFT SKEWED OR RIGHT SKEWED data patterns we prefer to describe the data using the FIVE NUMBER SUMMARY (mnimum, 1st quartile, median, 3rd quartile and maximum)
  1. For Exam 1 scores, which of the descriptors listed below are preferred:

MeanStdDev ______OR

Five Number Summary ______and why______

  1. For Exam 3 which of the descriptors listed below are preferred:

Mean & StdDev ______OR

Five Number Summary ______and why______

  1. Print the part of your spreadsheet showing histograms, descriptive statistics and quartiles and turn it in with your answers to the questions above. You do not need to print all of the data.
  1. SAVE YOUR FILE.

Updated August 22,2008