Answer :
The IQ score that marks the 90th percentile, using the Wechsler Test norms, is 119.2. This is found by converting the 90th percentile to a z-score (approximately 1.28) and using it in the formula IQ = mean + (z-score * standard deviation).
The question is asking to find the indicated IQ score that marks the 90th percentile for adults, using the Wechsler Test characteristics where IQ scores are normally distributed with a mean of 100 and a standard deviation of 15. In a normal distribution, the 90th percentile corresponds to a z-score value, which we find using a standard normal table or a calculator with z-score functionality.
To find this IQ score, we convert the percentile to a z-score and then use the formula for converting a z-score into an IQ score.
First, we find the z-score that corresponds to the 90th percentile, which typically is about 1.28. Using the z-score formula IQ = mean + (z-score * standard deviation), we calculate:
IQ = 100 + (1.28 * 15) = 100 + 19.2 = 119.2.
Hence, the IQ score that marks the 90th percentile is 119.2.
