Based on the data you have and the z table, what percentage of people might start to show signs of dementia at or before age 65?

Based on the data you have and the z table, what percentage of people might start to show signs of dementia at or before age 65?

(65-69.8)/2.79 = 1.72 = .44 =44%

If you consider the normal range of onset in this population to be +/-1 z-score from the mean, what two ages correspond to this?

Answer (+1 z)   Work: 2.79(1) + 69.8 = 72.59

Answer (-1 z)  Work: -2.79(1) + 69.8 = 67.01