Question

An ecologist is examining whether the number of fish caught in a large river basin has changed since a fire burned some of the surrounding forested area and vegetation along the river. Data in the form of fishing reports was available for a five-year period before the fire. From a random sample of 195 fishing reports before the fire, the mean catch was 6.3 fish with a standard deviation of 1.6. In a random sample of 143 reports three years after the fire, the mean catch was 7.1 fish with a standard deviation of 2.1.

Which of the following represents the standard error of the difference in the mean number of fish caught before and after the fire?

Answer 1

The standard error of the difference in the mean number of fish caught before and after the fire is 0.2153.

or

sqrt [ (1.6^2)/195 + (2.1^2)/143 ]