1 1a Generator — 1m. 3-valued — 1o. 1oa advanced 2 2a Mastery Envelope 3 3a Predictor 4 4a Ruling 5 5a Learning 6 6a Expectation 6b. special 6.1a. advanced 7 7a Last Test 8 8a Strategy 9 9a True Utility
Clicking the Go button will start a new simulation and/or analysis using the values specified in the menu.
exception: using option 1 to leave the analysis out, and next another option, the analysis will take affect ony at the second ‘Go.’
Because the applet is in a scrollable window, scrolling will cause the applet to execute again. Remember this whenever you declare a larger number of runs or observations. Eventually I might make the applets available in stand-alone format. Such as spa_applet1.sa.htm
The simulation simulates test scores for the specified number of observations or cases, assuming mastery having the value specified; the resulting distribution of test scores will be plotted as a solid green bar diagram. For larger numbers of observations the simulation will will be closer to the binomial distribution plotted in blue. If you want the analysis only, turn the simulation offf by putting the number of observations = 0.
The analysis evaluates a probability distribution function called the binomial distribution; the distribution plotted is this mathematical distribution. The binomial distribution is the theoretical distribution of test scores given a particular mastery, for the number of observations growing very large. If you want the simulation only, put option = 1 to turn the analysis off.
Mastery may be chosen between 0 and 1; mastery as a concept is defined on the set of test items that every concrete test is supposed to have been sampled from: it is the proportion of items the candidate would answer correctly if given the opportunity to try alle items in the domain.
The number of test items is the length of the test; this number is not limited.
The number of observations or runs is the number of runs for the simulation, or, equivalently, the number of cases or persons that is represented in the simulated distribution.
The reference point is a particular test score that is of interest to the user of the applet. It might be the cutoff score in pass-fail testing, the minimum score that is still considered to be a level of sufficient mastery, etcetera. It is marked by a solid vertical in the plot. Its value may be set at 0.
The horizontal scale is that of test scores obtained, the lowest score being 0.
The vertical scale as a default will be automatically chosen and depends on the highest value of the analytical distribution, this point is tabmarked. The vertical values are frequencies in the case of simulations, and probabilities in the case of analyses. Their values may be plotted using option 203 and 204, respectively. Of course frequencies and probabilities will be comparable. In fact, option 2 will plot the vertical differences separately.
The statistics reported are the mean and standard deviation for every distribution. Because the theoretical value of the binomial statistics assumes the number of observations to be infinite, there will be small differences between the actual statistics and the statistics obtained by evaluating their formulas. Simulation and analytical statistics will differ from each other, of course; the differences wil be smaller the larger the number of observations is chosen.
If you come across an applet that is not functioning properly, please mail me. It is not possible always to check all applets for unintended consequences of changes in classes. As this is a project in progress, such changes are made on a routine basis.
Applets are known to work correctly under:
Internet Explorer under Windows XP
Firefox 1.0.7 under Windows XP
Safari 1.2 under MacOSX 10.3.9
FireFox 22.214.171.124 under MacOSX 10.3.9
It might be the case that the applets do not open properly in browsers under Windows, or in browsers other than Safari under MacOS X: the applet field remains gray or blank.
In module chapters original applets have been replaced with screenshots; therefore applet problems should not hinder readers of the SPA project. Readers not able to use the applets in their browser, and yet willing to do so, may contact me, if preferences of the browser pertaining to Java do not seem to be the problem.
Information about Java, and applets in particular:
MacOS X: There is a problem with Java versions 1.4 for browsers other than Safari. See http://javaplugin.sourceforge.net/Readme.html; http://developer.apple.com/documentation/Java/Conceptual/Java131Development/deploying/chapter_3_section_5.html; simile.mit.edu/repository/ misc/java_embedding_plugin/readme.rtf
MacOS X: Opera, version 8.5, produces 'java.lang.UnsupportedClassVersionError: Spa_BinomialApplet (Unsupported major.minor version 48.0)
MacOS X: Internet Explorer 5.2 for Mac, [preferences: enable Java on; cookies: never ask; web content: enable plug-ins on] produces 'java.lang.UnsupportedClassVersionError: Spa_BinomialApplet (Unsupported major.minor version 48.0)
Windows: Java Applet plug-in makes it possible for your computer (including Windows® XP, Me, NT, 2000, 98, or 95) to run applets in your browser. http://www.mcdonalds.com/search/help/plug_play/sunmicro.html
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