The level of pesticides found in the blubber of whales is a

The level of pesticides found in the blubber of whales is a measure of pollution of the oceans by runoff from land and can also be used to identify different populations of whales. A sample of 8 male minke whales in the West Greenland area of the North Atlantic found the mean concentration of the insecticide dieldrin to be x = 347 nanograms per gram of blubber (ng/g). Suppose that the concentration in all such whales varies Normally with standard deviation = 58 ng/g.

Give a 95% confidence interval to estimate the mean level of dieldrin. (Round your answers to two decimal places.)
---- to ----- ng/g

Solution

Confidence Interval
CI = x ± Z a/2 * (sd/ Sqrt(n))
Where,
x = Mean
sd = Standard Deviation
a = 1 - (Confidence Level/100)
Za/2 = Z-table value
CI = Confidence Interval
Mean(x)=347
Standard deviation( sd )=58
Sample Size(n)=8
Confidence Interval = [ 347 ± Z a/2 ( 58/ Sqrt ( 8) ) ]
= [ 347 - 1.96 * (20.51) , 347 + 1.96 * (20.51) ]
= [ 306.81,387.19 ]