Frequency distributions and graphs; Data description

This week we will be calculating descriptive statistics for the discussion forum.

The main ones we will want to focus on are Mean, Median, Standard Deviation

(SD) and count. But I will show you how to get much more using the Data

Analysis ToolPak. If you haven’t installed this I encourage you to check out the

previous PDF and install this ASAP.

The first thing we want to do is put our data into Excel. Below I have Car Price

data that I gathered.

To find the Mean, Median, SD and Sample Size in Excel we will be using these

functions:

=AVERAGE( ) =MEDIAN( ) =STDEV.S( ) =COUNT( )

In the cell next to where it says Mean: you will first type in the “ = ” and then

“average” and click on the “ ( “. Then you will highlight the column of data, click

on the “ ) “ and click Enter.

Once the cell looks like this:

You will click Enter and you will end up with:

Once the cell looks like this, click Enter and you will end up with:

We see the mean car price is $25,650.

You will follow the same steps for the Median, SD and Sample Size.

The Median car price is $25,000

The SD of car price is $3,488.47

The sample size is 10. We should know this, but it is good to know how to find it

using Excel.

These are the descriptive statistics you will need for the discussion forum in Week

2, along with future weeks. But we can calculate lot more descriptive statistics

using the Data Analysis ToolPak in Excel. Since the ToolPak is already installed

you can go to Data - > Data Analysis

When you click on this a new window pops up:

You will want to find where it says “Descriptive Statistics” in the box, highlight it

and click “OK”.

Once you do that, another window will appear.

Where it says Input Range: you will want to highlight your Car Price data,

including the top row where it is labeled Car Price:

Then you will want to make sure the “Labels in first row” box is checked, because

that is where the Car Price label is located, the “Summary statistics” box is

checked and the “Confidence Level for Mean” box is checked. You can leave the

95% in the box for now. This value will be important when we discuss confidence

intervals and hypothesis testing in the coming weeks. You will want to check the

circle for Output options: “New Worksheet Ply”. Once all this is checked and it

looks like the screenshot above, click OK.

In a new tab this will populate:

Here we see the mean, median, standard deviation and count. These values

should match up with what we calculated previously. We also have new

descriptive statistics. The Standard Error (SE), Median, Sample Variance and

Range to name a few. By now you should have a good understanding on what

descriptive statistics are, how to analyze them and now how to calculate them.

At the bottom we see the Confidence Level (95.%) is given. This value is known as

the Margin of Error for a 95% Confidence Level. Again, you don’t have to worry

about this value during Week 2 but it will be discussed again when we talk about

confidence interval and hypothesis testing. It will be good to know how to

calculate when the time comes.