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This FLASH based applet illustrates the sampling distribution of the mean. This applet allows the user to pick a population from over 2000 pre-defined populations. The user can then choose size of the random sample to select. The applet can produce random samples in one, 10, 100, or 1000 at a time. The resulting means are illustrated on a histogram. The histogram has an outline of the normal distribution and vertical lines at 1, 2, and 3 standard deviations. The applet can be viewed at the original site or downloaded to the instructors machine.
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Date Of Record Creation 2008-01-26 17:00:00
Date Last Modified 2008-01-26 17:00:00
Date Of Record Release 2008-01-26 17:00:00
Alternate Title CAUSE Webinar March 2006 T & L
Email Address,
Date Issued 1998
Resource Type
Typical Learning Time 4 lessons
Author Name Michael C. Thomsett
Author Organization Center for Technology and Teacher Education
General Comments Dead link. Web site appears totally gone and cannot find alternatives.
Technical Requirements Flash
Comments There is a copyright and cost for StatCrunch, but not for the webinar. Please see for details.
Content Quality (Concerns) In some discrete distributions (e.g. binomial, Poisson) the left/right/between probabilities change continuously as the endpoint is dragged within the "bar" for a single discrete value - as if it were a continuous variable. Automatic axis rescaling makes it difficult at times to see the effect of changing a parameter with a slider. A number of distribution options are listed in the menu but not yet implemented.
Content Quality (Strengths) The key strengths of this applet include the consistent interface for all distributions. It also includes depictions for an extremely lengthy list of distributions.
Ease of Use (Concerns) Mouse resolution can make it difficult to get an endpoint precisely. For example, in finding a p-vlaue for a t.s.=2.18, student might have to "settle" for endpoint of 2.172 or 2.19. This resource could be greatly enhanced by allowing students to put in a specific value rather than trying to find it with the mouse. This is especially important for students who will replace traditional tables with this applet. Although you can enter values for parameters in a text box you must hit enter to have it recorded. Just typing it in and tabbing to different field or clicking on a different box appears to leave the parameter unchanged - even though the typed value is changed. Default parameters on some distributions are not reasonable - eg. p=0.0 is shown by default for a geometric, when p-0.05 is apparently plotted. The applet includes a snapshot feature that should take a screen shot of the applet. However, the reviewers could not get this feature to work.
Ease of Use (Strengths) Users can easily change the shaded area of a distribution by dragging endpoints. This works fairly intuitively and will help students visualize the connection between probabilities and the density/probability function. Sliders allow easy specification/modifications of parameters.
Potential Effectiveness (Concerns) Long list of (40+) potential distributions may be intimidating to a beginner student who might just need normal and t-distributions. Listing of (endpoint, density function value) pair as one scrolls along a density curve might confuse a student to read the density as a probability (as it is for a discrete random variable).
Potential Effectiveness (Strengths) The consistent interface allows students to "look-up" p-values and critical values with the same basic tool for all distributions. This applet is good way to easily "see" lots of distributions and how the parameters affect their shape. This may allow courses to include more distributions than the traditional binomial, normal, and t-distribution. For more advanced students, the links to find out more about each distribution (from Wolfram's Mathworld) are a nice touch.
Source Code Available 1
Material Type
Statistical Topic
Application Area
Cost involved with use
Intended User Role
Math Level

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