The mean of a normal probability distribution is 340 the sta

Solution

Given that the mean (u) of a normal probability distribution is 340 and the
standard deviation (sd) is 14.
(a) About 68% of the area under the normal curve is within one standard deviation of the mean. i.e.
(u ± 1s.d)
So to the given normal distribution about 68% of the observations lie in between
= (340 ± 14)
= [326, 354]

(b)
About 95% of the area under the normal curve is within two standard deviations of the mean. i.e.
(u ± 2*s.d)
So to the given normal distribution about 68% of the observations lie in between
= (340 ± 2*14)
= [312, 368]

(c)
Practically all of the area under the normal curve is within three standard deviations of the mean. i.e.
(u ± 3*s.d)
So to the given normal distribution practically all of the observations lie in between
= (340 ± 3*14)
= [298, 382]