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?
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Since you are given the mean (average) and standard deviation, this is clearly a normal distribution.
The mean is 400 and the standard deviation is 20 mg
Therefore, the "standardized variable" = (390- 400)/20 = -0.5
Remember (390 is 1/2 standard deviations below the mean).
We can now use a table of the standard normal distribution to look up the probability that z< -0.5.
The answer comes to;
0.10564
The mean is 400 and the standard deviation is 20 mg
Therefore, the "standardized variable" = (390- 400)/20 = -0.5
Remember (390 is 1/2 standard deviations below the mean).
We can now use a table of the standard normal distribution to look up the probability that z< -0.5.
The answer comes to;
0.10564
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