At a local restaurant, the amount of time that customers have to wait for their food is normally distributed with a mean of 22 minutes and a standard deviation of 3 minutes. If you visit that restaurant 37 times this year, what is the expected number of times that you would expect to wait between 19 minutes and 23 minutes, to the nearest whole number?
Q. At a local restaurant, the amount of time that customers have to wait for their food is normally distributed with a mean of 22 minutes and a standard deviation of 3 minutes. If you visit that restaurant 37 times this year, what is the expected number of times that you would expect to wait between 19 minutes and 23 minutes, to the nearest whole number?
Given Information: We are given that the wait time for food at a local restaurant is normally distributed with a mean μ of 22 minutes and a standard deviation σ of 3 minutes. We want to find the probability of waiting between 19 and 23 minutes.
Standardize Wait Times: First, we need to standardize the wait times of 19 minutes and 23 minutes using the z-score formula: z=(X−μ)/σ, where X is the value from the normal distribution, μ is the mean, and σ is the standard deviation.
Calculate z-score for 19 minutes: Calculate the z-score for 19 minutes: z=(19−22)/3=−3/3=−1.
Calculate z-score for 23 minutes: Calculate the z-score for 23 minutes: z=323−22=31≈0.33.
Lookup z-scores in table: Now, we look up these z-scores in the standard normal distribution table or use a calculator to find the probabilities. The probability of z being less than −1 is approximately 0.1587, and the probability of z being less than 0.33 is approximately 0.6293.
Find probability of waiting: To find the probability of waiting between 19 and 23 minutes, we subtract the probability of waiting less than 19 minutes from the probability of waiting less than 23 minutes: P(19 < X < 23) = P(X < 23) - P(X < 19) = 0.6293 - 0.1587 = 0.4706.
Calculate expected number of times: Now, we multiply this probability by the number of visits to find the expected number of times you would wait between 19 and 23 minutes: Expected number of times = Total visits × Probability = 37×0.4706.
Round to nearest whole number: Calculate the expected number of times: Expected number of times = 37×0.4706≈17.4122.
Round to nearest whole number: Calculate the expected number of times: Expected number of times = 37×0.4706≈17.4122.Since we cannot visit a fraction of a time, we round to the nearest whole number: Expected number of times ≈17 (to the nearest whole number).
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