Title: Interactive Chapter 4 Parts 1 & 2
Course: PSYC 301 Statistical Methods in Psychol > Section: First Part of Course

This is an activity using the application GeoGebra by the prolific creator on GeoGebra: Steve Phelps.

The goal here is for you to adjust values of the data on the number line below and notice how the standard deviation (SD) and mean (Red dot), change as you move them.

Recall that the concept of the mean is a middle point that, if you add up all the distances from it to the individual pieces of data, would yield a value of zero (distances to the left are negative numbers for that calculation).

Recall that the concept of the standard deviation is, roughly, the average distance the scores are spread above and below the mean. So, the value of it is from the mean above and from the mean below (the negative direction).

After sliding the various values around, slide the dots for points A and E to be 5 units below and above the mean, respectively. If that's hard to do, reload the page to get a new set of numbers. AFter setting A and E that way, don't touch them. Write the value of the standard deviation. Move dots B, C, and D to be quite close to the mean, maybe right on top of it. Notice what happens to the standard deviations. Even though the maximum and minimum values haven't changed (meaning the range hasn't changed) the standard deviation has gotten smaller.

Imagine what would happen if all the scores were at the mean? What would happen to the standard deviation? Highlight by dragging to select the following text to see the answer: it would be zero.