Title: Interactive Ch 4 Pt 1
Course: PSYC 301 Statistical Methods in Psychol > Section: First Part of Course

This is an interactive activity designed to help you conceptualize some of the ideas about the mean. It is by KK Ip and sonom on GeoGebra.

First let me tell you how the app works. In the app window, below all these instructions, you'll see a blue box and a box with gold Xs.

You will be clicking and dragging the Xs from their location to the number line. When you place one a number will appear next to it. That number is the number line value you placed that X on. You can move it around by clicking and dragging it. Note that if you put two Xs at the same location, one above the other, you now have two values indicated as part of your dataset (a collection of data).

That is similar to a kind of graph called a dot-plot. The number of dots indicates the number of those values in the dataset. Below is a screen snap that shows a dataset composed of two scores of 3, two scores of 4, three scores of 5, and two scores of 6.

You'll also see a gold slider in the lower right. Slide the slider all the way to the left so that the number line reads 10. Now, drag one X over to the score of 3 and another over to the score of 4. Think about what you know about the Mean, Median, and Mode and decide what those scores should be. This is easy enough math that you can do it in your head. When you've decided your answers and committed them to paper:

Highlight the text to the right to see the correct answer: Mean = 3.5, Median = 3.5, Mode = No Mode. The reason for no mode is there is no value that happens more than any other. End of highlighting.

Unclick the three measures of center. Now drag another X over to 5, still another to 4. Do the same thing to think about what the Mean, Median and Mode are. When you've got your answers committed, click the boxes to see what they should be and highlight to the right: Mean = 4, Median = 4 and Mode = 4. If you wrote mode equal 2 then you were incorrect. The mode is the score that happens most frequently. End of highlighting.

Now, leaving the three boxes clicked, click and drag the X that is set for a value of 5 to a larger value and watch the mean, median and mode change (or not change). Note that the median and mode don't change, only the mean changes. Think about why that may be the case. Highlight for the answer. The mean is calculated by using the actual values added up, which changes as the scores change. The median is simply the count of values above and below a middle point which doesn't change as you slide the highest value to a higher value. The mode is the most frequently occurring value, which doesn't change unless you happen to put that 5 on top of another value that is higher, making that the new most frequent value. End of highlighting.

Finally, notice that the answer for Mode is in brackets. That's because it's possible to have datasets that have multiple values that have the same high frequency, therefore, both are modes. Modes are weird.