An IQ test has a mean of 97 and a standard deviation of 5. Which is more unusual, an IQ of 107 or an IQ of 84?
An IQ of _____is more unusual because its corresponding z-score, ________
is further from 0 than the corresponding z-score of _______ for ________.
If a random Variable X has mean and standard deviation , then the Z score for any value of X is =
Here , = 97 and = 5
For , X = 107 , Z =(107-97)/5 = 2
For, X = 84 , Z = (84-97)/2 = -2.6
We know for any observation Z score should be close to 0 to be a usual observation.
Here an IQ of 84 is more unusual because it's corresponding Z score -2.6 is further from 0 than the corresponding Z score of 2 for 107
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