 Hi folks, this is Dr. Don. I have a problem from Chapter 2 about measures of central tendency. Specifically, we're going to be finding the mean and median and seeing how they change as the data set changes. In the problem, we're given a table of data of exports from a country to 19 other countries. As I scan down the problem, I see that we're going to be deleting one country from the list and recalculating the mean and median to see what changes result. Then we're going back to the original data with all 19 countries and adding a 20th country's exports and again comparing the mean and the median. Although you could do this problem with StatCrunch, when I have to make changes to a data set, I usually find that Excel is easier to use and I can keep copies as I usually do to compare what happens when I make the changes. Let's start by clicking in the blue rectangle to open the data. To get the data in Excel, I'm going to click on the second blue rectangle and select Open in Excel. Okay, I have Excel open with the data in column B with the names of the countries in column A. I've added labels in cells C2 and C3 for the mean and the median. To find the mean in Excel, we use the Average function. Click in cell D2 and enter an equal sign and start typing Average. Then double click on Average to select that function. When I know I'm going to be changing a data set, I use a trick to set the range. Instead of selecting the actual cells, I'm going to use the range B colon B to select everything in column B because I know there's nothing else in this new workbook. The Average function knows to only pay attention to cells that actually have a number and it finds the correct average or mean automatically. It is $58.68 billion of exports. To find the median, we use the median function. Start typing median in cell D3 and then double left click to set the median function. Again, I'm going to use the open range method for the median. We find the median is $29.90 billion. Part B of the problem says to find the mean and median again, but without country A's exports. To do that in Excel the way I have set it up, all I need to do is to delete the value for country A like this. We see the mean and the median both change automatically. But now I cannot see what the original values were to be able to see which one changed more. So I'm going to undo the deletion of country A by clicking on the undo icon in the upper right here. Now I'm going to make a copy of this part A by selecting this area. Then I'm going to right click and click copy. I'm going to paste the copy here in cell F1. Everything works because I just used relative cell references in my formulas. Now I can delete country A and see the results. The mean drops about $12 billion, but the median barely changes. That is because the exports to country A were so large compared to most of the other countries. Remember the mean is always impacted more by extreme values than the median as we can see here. In part C we are to add in the exports of country Z of $21.7 billion to the original data set. Again, so I can see the other two parts. I'm going to make a third copy of the data and calculations using the same method. This time I'm going to paste it into cell K1. I can add the $21.7 billion at the bottom because I used the open range method. The mean drops a little, about $2 billion, but the median changes very little in comparison. Using Excel and making copies of the data and calculations sometimes let you more easily compare changes quickly. Hope this helps. If it does, be sure to subscribe to my YouTube channel by clicking the big red subscribe button.