A company that runs a chain of quick oil change centers, tries to attract customers by claiming that it completes oil changes faster than its competition. So it periodically estimates the time taken to do oil changes at its centers. From historical records, the company knows that the population standard deviation of oil change duration is 15 minutes. Recently, 40 customers were asked how much time they spent getting an oil change at one of their centers. Based on the sample data, the chain concluded that the average oil change time for the population of all its customers was between 15 and 25 minutes. What was the confidence level at which the inference was made? Think about the tradeoff among (n, confidence level, margin of error) and the formulae connecting the three. This time, you are given the margin of error and the sample size, and are asked to find the level of confidence. You will use the same formulas, just with a different unknown}.
A company that runs a chain of quick oil change centers, tries to attract customers by claiming that it completes oil changes faster than its competition. So it periodically estimates the time taken to do oil changes at its centers. From historical records, the company knows that the population standard deviation of oil change duration is 15 minutes. Recently, 40 customers were asked how much time they spent getting an oil change at one of their centers. Based on the sample data, the chain concluded that the average oil change time for the population of all its customers was between 15 and 25 minutes. What was the confidence level at which the inference was made? Think about the tradeoff among (n, confidence level, margin of error) and the formulae connecting the three. This time, you are given the margin of error and the
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