A 95 confidence interval for the mean number of species in a

A 95% confidence interval for the mean number of species in a one hectare plot for an area of tropical rainforest is (40, 52). If 36 one hectare plots were sampled, the standard deviation of the number of species in plots is most likely:

Question 4 options:

12

6

18

3

5

Solution

Given a=1-0.95=0.05, Z(0.025) = 1.96 (from standard normal table)

The margin of error:

Z*s/vn = (52-40)/2 =6

--> 1.96*s/sqrt(36) =6

--> 1.96*s/6 = 6

So standard deviation = 6*6/1.96 =18.36735

Answer: 18