Empirical Rule. It is known that the lengths of trout in a particular river are approximately mound-shaped with mean 14” and standard deviation 1”. About what proportion of the trout have lengths between 11' and 14' and 14” and 16”?
Answer)
According to the emperical rule
If the data is normally distributed
Then 68% lies in between mean - s.d and mean + s.d
95% lies in between mean - 2*s.d and mean + 2*s.d
99.7% lies in between mean - 3*s.d and mean + 3*s.d
Given mean = 14
S.d = 1
11 = 14 - (3*1)
17 = (14 + (3*1)
So, 99.7% lies in between 11 and 17
As normal distribution is symmetrical about mean
So, 99.7/2 = 49.85% lies in between 11 and 14
Between 14 and 16
16 = 14 + 2*1
So, 95/2 = 47.5% lies in between 14 and 16
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