## Step 3: Explore the Data

After collecting the data, Step 3 in a Statistical Investigation is to produce numerical and graphical summaries of the sample data. The goal is to discuss the overall patterns in the data. Here we donâ€™t want to just present a bunch of "Tim" and "Bob" outcomes but a simple number and a picture or two that best represents what we learn from the data.

Taking the observational unit to be one student from class, we can define the variable as *which name was put on the left*, which is categorical and binary. The *sample size *is the number of observational units we have data for, so in this case, it equals the number of students who responded to our question in class.

### Graphical Summary, Statistic

With a binary categorical variable, we arbitrarily define one outcome to be "success" and the other to be "failure." We can then use *either* the number of success or the proportion of successes as the *statistic*.

To graph the data, we use a simple *bar graph*. We will use a different applet than in Lab 0 to explore these categorical data.

- In the Excel file, click on the letter A above variable name "NameOnLeft" to highlight the entire column.
- Right click and select Copy (or ctrl-C) and then in the applet below, check the
**Paste Data**box and the**Includes header**box, press**Clear**and then right click and select Paste (or ctrl-V) to paste the data into the box. Press the**Use Data**button.

(a) Create a screen capture of your output (in the picture include both the summary data = (sample size *n*, count of successes, proportion of success , and the graph).

Also enter the values for below for later reference in the lab.