Age at onset of dementia was determined for a sample of adults between ages of 60 and 75. For 15 subjects, the results were EX=1008, and E(X-M)square root=140.4. Use this formula to answer:
Mean and standard deviation:
What percentage of people might start to show signs of dementia at or before age 62 based on the data and and the Normal Curve Tables?
If we consider the normal range of onset in this population to be +/-1 z-score from the mean, what two ages correspond to this?
A neuropsychologist is interested only in studying the most deviant portion of this population, that is, those individuals who fall within the top 10% and the bottom 10% of the distribution. She must determine ages that m ark these boundaries What are these ages?