If the mean plasma-aldosterone level in African American children was 230 pmol/L with a standard deviation of 203 pmol/L, then what percentage of African American children have levels ≤ 300 pmol/L if normality is assumed?

Hypertension
Well-known racial differences in blood pressure exist between Caucasian and African American adults. These differences generally do not exist between Caucasian and African American children. Because aldosterone levels have been related to blood-pressure levels in adults in previous research, an investigation was performed to look at aldosterone levels among African American children and Caucasian children [2].