An ecologist is examining whether the number of fish caught in a large river basin and 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?