Question

One 16-ounce bottle of an energy drink has an average of 400 mg of caffeine with a standard deviation of 20 mg. What is the probability that the average caffeine in a sample of 25 bottles is no more than 390 milligrams?

a) 0.006

b) 0.004

c) 0.002

d) 0.001

Answer 1

Solution :

Given that,

mean = = 400

standard deviation = = 20

n = 25

= 400

₌ / n = 20 25 = 4

P ( 390 )

P ( - /)   (390 - 400 /4)

P( z   - 10 / 4)

P ( z -2.5 )   

Using z table

= 0.0062

Probability = 0.006

Option a ) is correct.