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- May 29, 2014
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Hi I'm trying to understand how standard deviation distribution works. I think i know what standard deviation is and how it works but i'm really confused about the distribution.
when you set the first and second standard deviation, how you get that 5% and 2.5%?
I did search it but the numbers are somewhat different. (they told me it's 19% for the first and second 15%)
Can anyone help me out? Thanks.
The average IQ of the city of Gotham is 110, and the standard deviation is 15. If the city has a population of 15,000, what would be a reasonable number of people whose IQ is above 140?
Given a mean of 110 and a standard deviation of 15, we see that 125 is the edge of the first standard deviation, and 140 is the edge of the second standard deviation. Since we know that only 5% of people fall outside the 2nd standard deviation, we find that only 2.5% have an IQ above 140. Remember that the other 2.5% falls into the lower range, of people below an IQ of 80. Thus, 2.5% of 15,000 is 375 people, which is answer [C].
when you set the first and second standard deviation, how you get that 5% and 2.5%?
I did search it but the numbers are somewhat different. (they told me it's 19% for the first and second 15%)
Can anyone help me out? Thanks.
The average IQ of the city of Gotham is 110, and the standard deviation is 15. If the city has a population of 15,000, what would be a reasonable number of people whose IQ is above 140?
Given a mean of 110 and a standard deviation of 15, we see that 125 is the edge of the first standard deviation, and 140 is the edge of the second standard deviation. Since we know that only 5% of people fall outside the 2nd standard deviation, we find that only 2.5% have an IQ above 140. Remember that the other 2.5% falls into the lower range, of people below an IQ of 80. Thus, 2.5% of 15,000 is 375 people, which is answer [C].
