In: Statistics and Probability
A large tank of fish from a hatchery is being delivered to a lake. The hatchery claims that the mean length of fish in the tank is 15 inches, and the standard deviation is 6 inches. A random sample of 60 fish is taken from the tank. Let x be the mean sample length of these fish. What is the probability that x is within 0.5 inch of the claimed population mean?
a. .5000
b. .4814
c. .1467
d. .0325
Solution :
Given that,
mean = = 15
standard deviation = = 6
n = 60
= = 15
= / n = 6 / 60 = 0.7746
P(14.5 < < 15.5)
= P[(14.5 - 15) /0.7746 < ( - ) / < (15.5 - 15) / 0.7746)]
= P(-0.6455 < Z < 0.6455)
= P(Z < 0.6455) - P(Z < -0.6455)
Using z table,
= 0.7407 - 0.2593
= 0.4814
correct option is = b