This site includes several applets and QuickTime movies to illustrate several statistical concepts. One particular applet that was reviewed carefully displays the normal distribution, and users may choose mean and standard deviation parameter values and observe the effect on the center and dispersion of the distribution. Other resources/applets on this site cover topics such as the binomial distribution, the poisson distribution, the central limit theorem, regression, and correlation.
Type of Material:
Learning objects/Collection
Recommended Uses:
These movies or the applets could be used in class by the instructor to give the students a better understanding of the specific statistical concepts or even out of class. These resources may be more appropriate as in-class demos since they sometimes require explanation that are not present on the website.
Technical Requirements:
Java required. Ran well on Firefox, Chrome and IE. Need QuickTime to view videos.
Identify Major Learning Goals:
Students can see the normal distribution plotted for many values for the mean and standard deviation. Students can also learn about other distributions (such as the binomial and poisson distributions) and the central limit theorem. There are also links to regression and correlation applets.
Target Student Population:
Introductory level statistics students, at the high school or college levels.
Prerequisite Knowledge or Skills:
Students should understand probability distributions and measures of central tendency and variation.
Content Quality
Rating:
Strengths:
The movies and the applets are a good source of demonstrating the statistical concepts and they are easy to use. The normal distribution applet (in particular) demonstrates how changing the mean (location) parameter and standard deviation (scale) parameter affects the location and spread of the normal distribution.
Concerns:
In some ways, the site lacks clear presentation. As an example, under the “Graphs of the normal distribution” page, it would have been better if the hyperlink “QuickTime clip of the normal distribution” is reworded as “Quicktime clip: changing the standard deviation of the normal distribution” and also for it to appear on the same page as the “Quicktime clip: changing the mean of the normal distribution." Then the viewers have clear and easy access. A much clearer writing style is suggested.
There is only a limited range of means for the normal distribution to view (from -2.0 to 7.0). The normal curve is either partially viewable or not seen if you specify means far outside this range. This is easily explainable to the students however. On the other hand, when students were using this applet, some decided to try the value 0 for the standard deviation. Instead of giving an error (or somehow communicating that they would all be the same numerical value), it displayed a normal distribution with a standard deviation of 1.
Potential Effectiveness as a Teaching Tool
Rating:
Strengths:
The applets are very easy to use as teaching tools, The normal distribution applet easily demonstrate the effect of changing the mean / standard deviation of a normal distribution. The applet allows students to visualize the statistical concepts they learn.
Concerns:
There is not always a lot of guidance about how to use certain applets or what to do with them. For example, with the normal distributions applet, there could be some questions added such as “What happens to the distribution when the mean/standard deviation is changed?”, etc…. Also, due to the limited viewing range, many students were confused about “what happens” in the areas that are not seen.
Ease of Use for Both Students and Faculty
Rating:
Strengths:
This collection is of a very high quality design. It is ideal for the students to understand and visualize the concepts. Overall, the applets seem easy to get started with and begin exploring.
Concerns:
In the specific case of the normal distribution applet, there is a lack of views for specific values of the mean and standard deviation that could confuse students. The issue with the mean has already been discussed, but another problem occurs when the standard deviation gets quite close to zero. In this case, the top of the distribution is not viewable. In contrast, the distribution shape is harder to see when the standard deviation is large (as it gets cut off).
Creative Commons:
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