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The first exam in your Statistice course is garded on a scale of 0 to 100, and the mean is 76. Which value is most plausible for standard deviation :-20,0,10,or50?why? Grade point average of graducting seniors at the university of Rochester must fall between 2.0 and 4.0. Consider the possible standard deviation values-10.0,0.0,0.4,1.5,6.0 which is the most realistic value?why? Which value is impossible? Why?

The first exam in your Statistice course is garded on a scale of 0 to 100, and the mean is 76. Which value is most plausible for standard deviation :-20,0,10,or50?why? 10 Consider the possible standard deviation values-10.0,0.0,0.4,1.5,6.0 which is the most realistic value?why? 0.4 这两个琢磨一下 empirical rule [img]http://upload.wikimedia.org/wikipedia/commons/thumb/8/8c/Standard_deviation_diagram.svg/350px-Standard_deviation_diagram.svg.png[/img] Which value is impossible? -10 更简单了 .. 看下 stdev 的definition 就明白了 [img]http://upload.wikimedia.org/math/3/a/9/3a995705c12638ca89e78499b63fb568.png[/img]