Question

Samples of fish taken from the Spokane River were tested for lead content in milligrams per kilogram. Because most of the lead is thought to be concentrated in bones and fat, tests were carried out on filets, which are more representative of the fish that people actually consume. A sample of 22 rainbow trout filets had mean lead content 0.16 and standard deviation 0.11; a sample of 20 largescale suckers had mean 0.09 and standard deviation 0.06.

Use the formula x1 − x2 ± multiplier square root of (s1)^2/n1 + (s2)^2/n2 and the fact that the two-sample t multiplier for a fairly large combined sample size is approximately 2 to produce a 95% confidence interval for the difference between mean lead contents, trout minus suckers. (Round your answers to two decimal places.)

Answer 1

By the given information:

Margin of error

E = 0.05

Hence,

95% confidence interval will be:

(0.16 - 0.09 - 0.05, 0.16 - 0.09 + 0.05)

(0.02, 0.12