Question

Since a normal distribution is taken into account, what percentage of the distribution values will fall in the range of a standard deviation below and above the mean?
A -) %68
B -) %50
C -) %99.7
D -) %99.5

Answer 1

Z value for a standard deviation below the mean =-1

Z value for a standard deviation above the mean = +1

from normal distribution curve:

P(Z=-1) =0.1587

P(Z=+1) =0.8413

a standard deviation below and above the mean = P(Z=+1) -P(Z=-1)

a standard deviation below and above the mean = 0.8413-0.1587=0.6826

a standard deviation below and above the mean = 68.26%

ie., a standard deviation below and above the mean = 68%

Option -A