Question

In a recent study of animal sleep times at the zoo, the mean amount of sleep per night is 6.3 hours with a standard deviation of 2.1. If 23 animals are selected, find the probability that the mean sleep time per night is greater than 8 hours.

0.0103
0.2981
0.3207
0.0001

Answer 1

Using the same reasoning as in your other question (26611591),

Pr[X > 8] = Pr[(X - 6.3) / (2.1 / √23)) > (8 - 6.3) / (2.1 / √23)]

… ≈ Pr[Z > 3.8823]

… ≈ 1 - Pr[Z ≤ 3.8823]

… ≈ 0.0000517281

… ≈ 0.0001

Answer 2

0.001

hope this helped a bit!