Statistics
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Statistics
Chapter 5
Number 5.11
In any typical problem, the access to a standard normal table is gained through a z-score and the answer is read as a proportion. To this end, therefore, to determine the proportion of IQ scores on a Wechsler Adult Intelligence Scale (WAIS) in an approximated normal curve that has a mean of 100 and standard deviation of 15, then all we have to do is to determine the z-score. In the determination of the z-score, the original provided score is expressed as a deviation from its mean after which the deviation is split into standard deviation units. Therefore;
* The proportion of IQ scores above Kristen’s 125 is calculated as;
=(Original Score-Mean)Standard Deviation
=125-10015
= 1.6667
* The proportion of IQ scores below 82 is calculated as;
=(Original Score-Mean)Standard Deviation
=82-10015
= -1.2
* The proportion of IQ scores within 9 points of the mean is calculated as;
