Well-known racial differences in blood pressure exist between white and black ad

Question

Well-known racial differences in blood pressure exist between white and black adults. These differences generally do not exist between white and black 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 black children and white children. 7.

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

Explanation / Answer

We first get the z score for the critical value. As z = (x - u) / s, then as          
          
x = critical value =    300      
u = mean =    230      
          
s = standard deviation =    203      
          
Thus,          
          
z = (x - u) / s =    0.344827586      
          
Thus, using a table/technology, the left tailed area of this is          
          
P(z <   0.344827586   ) =    0.634888 = 63.49% [ANSWER]

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