Question

a)

LC50 for a chemical is the lethal concentration for 50% of animals or humans. For example, if water contains a chemical at the LC50 concentration, 50% of the fish population in the water would die. Environment Canada collects data on LC50 concentrations. A 95 % confidence interval for the true mean LC50 with a random sample of 61 is (15.8, 18.4). Suppose the chemical concentration is measured in a local lake and found to be 19. This means that

Group of answer choices

the proability that all of the fish will dies is less than 50%.

the probability that 50% of the fish will die is more than 95%.

the probability that 95% of the fish will die is more than 50%.

at least 95% of the fish will die if nothing is done.

it is very likely that 50% of the fish will die if nothing is done.

b)

Suppose the mean of a population distribution is μ. The average of a sample from the distribution of size n is x ¯ and the sample standard deviation is S. Which quantity below has a t distribution?

Group of answer choices

X¯−μS/nX¯−μS/n

μ−x¯S/nμ−x¯S/n

X¯−μsX¯−μs

Answer 1