Answer:
95% of the customers have to wait between 10 minutes and 26 minutes
Step-by-step explanation:
We are given the following information in the question:
Mean, μ = 18 minutes
Standard Deviation, σ = 4 minute
We are given that the distribution of amount of time is a bell shaped distribution that is a normal distribution.
Empirical Formula:
- Almost all the data lies within three standard deviation from the mean for a normally distributed data.
- About 68% of data lies within one standard deviation from the mean.
- About 95% of data lies within two standard deviations of the mean.
- About 99.7% of data lies within three standard deviation of the mean.
Now, we can write:
Thus, by empirical formula, 95% of the data lies within two standard deviations of the mean.
Thus, 95% of the customers have to wait between 10 minutes and 26 minutes