LAB 1
DESCRIBING DATA GRAPHICALLY
INSTRUCTIONS & QUESTIONS
NAME________________________LAB TIME________________LAB BLDG________________
1.
Go the the Stat301T webpage, (www.stat.purdue.edu/~jdobbin/stat301T) . Click on Lab
Instructions, Questions and Data. Open the instructions and questions file and print it. Then click
on the Lab1 data file and save it in your own directory. Then start Microsoft Excel 2003. DO
NOT START EXCEL 2007
2.
Then open the Lab 1 data file using Excel 2003.
3.
Scroll up to line 1 of the data file. Column A shows exam1 scores for Spring 04, and column B
shows exam 3 scores. Both columns are sorted in ascending order.
4.
Make histograms for column A and column B. Histograms are a good way to examine data
graphically. In Excel do: (Tools>Data Analysis>Histogram). If data analysis is not shown on the
menu, click on Tools>Add-Ins, and on the new window click on the first box to add in the
Analysis ToolPak and then click OK. Then go back and do: Tools>Data Analysis>Histogram.
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, click on options and change
GAP to 0. Repeat for Column B Histogram: input range (B2:B216), output range (C22).
5.
Describe both histograms with respect to shape, center, spread and outliers.
descriptor
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.
Exam 1 (column A)
Exam 3 (column B)
Spread: Fill in the minimum and the
maximum after you get the descriptive
statistics in Step 6.
minimum _______
minimum__________
maximum_______
maximum__________
Outliers, yes or no? Outliers are values
which look like they do not belong.
If “yes”, determine their value by looking at
the data which is in ascending order.
6.
Calculate descriptive statistics for column A and column B. (tools>data analysis>descriptive
statistics) .
7.
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
8.
Since the descriptive statistics do not include the 1st and 3rd quartiles, calculate these descriptors
for column A and B using the following steps: First Quartile is the 25th percentile (25% of the
way through the data), and the Third Quartile is the 75th percentile.
1)
Go to C57 and type 1st Quartile. Then go to D57 and type =.
2)
Go up to the tool bar, select quartile function, (might have to select more functions first)
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.
5)
Using the descriptive statistics output, fill in the Minimum and Maximum values in
Question 5 above for each data set.
9.
For SYMMETRIC data patterns we like to describe the data using two numbers, the MEAN (for
center value) and the STANDARD DEVIATION (for the spread going away from center)
10.
For LEFT SKEWED OR RIGHT SKEWED data patterns we prefer to describe the data using the
FIVE NUMBER SUMMARY (minimum, 1st quartile, median, 3rd quartile and maximum)
11.
For Exam 1 scores, which of the descriptors listed below are preferred:
Mean & StdDev ______ OR
Five Number Summary _______ and why________________________________________
12.
For Exam 3 which of the descriptors listed below are preferred:
Mean & StdDev ______ OR
Five Number Summary _______ and why________________________________________
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.
13.
14.
SAVE YOUR FILE.
Updated August 20, 2008