Recall that the Natural Resources Defense Council found that 25% of bottled-water brands fill their bottles with just tap water. In a random sample of 70 bottled-water brands, let x be the number that contain tap water.
Find the approximate probability that 25 or more of the 70 sampled bottled-water brands will contain tap water.
The answer is .0192 but i am unsure how to solve
mean=17.5
std=3.62
zscore=2.07
Solution:
We are given
n = 70
p = 0.25
q = 1 – p = 0.75
Mean = np = 70*0.25 = 17.5
Standard deviation = SD = sqrt(npq) = sqrt(70*0.25*0.75) = 3.622844
WE have to find P(X>25)
Z = (X – mean)/SD = (25 - 17.5)/ 3.622844 = 2.070197
P(Z<2.070197) = P(X<25) = 0.980783
(by using z-table)
P(X>25) = 1 - P(X<25) = 0.019217
Answer: 0.0192
Recall that the Natural Resources Defense Council found that 25% of bottled-water brands fill their bottles...
Is the bottled water you’re drinking really purified water? A study of various brands of bottled water conducted by the Natural Resources Defense Council found that 23% of bottled water is just tap water packaged in a bottle. Consider a sample of 15 bottled- water brands (sampled independently). What is the probability that at least 2 contain tap water?