malinda
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A particular association determines membership on the basis of members' IQ scores. Only those persons who
have documented IQ scores at least 2 standard deviations above the mean on the Wechsler Adult Intelligence
Scale (WAIS) are eligible for admission. Of a group of 200 people randomly selected from the population at
large, how many would be eligible for membership to this society?
A. 1
B. 2
C. 3
D. 4
E. 5
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| robin082006
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E
mean=100, SD=15
95% lie between 2 SDs, or 2.5% are over 2SD from the mean and 2.5% are under 2SD from the mean.
Therefore, 2.5%*200=5
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| malinda
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hmmmmm...okay
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| mazinger
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Ok this is an easier way to interpret this question... For answering this you MUST know how individuals are distributed in a random sample (gaussian curve). First you must know that in a "symetrical" distribution the central tendency (mean) is equal to the 50% of the subjects. The amount of individuals below 3 standard deviations of the mean are 0.15%, 2 S below 2.5%, 1 S below 15%, the mean as I said 50%, 1 S above 84%, 2 S above 97,5%, 3 S above 99,85%. So if the question asks how many individuals are bove 2 S of the mean, you just have to substract 100%-97.5%= 2.5% then you will just have to make a simple calculation to determine what's the 2.5% of 200 individuals; which in fact is 5.. Malinda last tip in order for you to answer this kind of questions you MUST KNOW from memory the numbers corresponding to a gaussian curve distribution.. Kaplan Behavioral Science book page 20, year 2002. As someone wrotte before "Listening to Dr. Daugherty's lecturres is IMPERATIVE". Best regards and good luck
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original mazinger z
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| malinda
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OH it means I need to learn the small numbers too...thanx a lot guys.
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