A random sample is used to estimate the mean time required for caffeine from pro

Question

A random sample is used to estimate the mean time required for caffeine from products such as coffee or soft drinks to leave the body after consumption. A 95% confidence interval based on this sample is: 5.6 hours to 6.4 hours (for adults) What is the margin of error? How many commuters must be randomly selected to estimate the mean driving time of Chicago commuters? We want 95% confidence that the sample mean is within 3 minutes of the population mean, and the population standard deviation is known to be 12 minutes. 8 commuters 7 commuters 62 commuters 61 commuters If we increase our sample size the width of the confidence interval will decrease stay the same

Explanation / Answer

Q4 Margin of error = (Upper limit - lower limit)/2 = 0.4

Q5

Margin of error = z * sigma /sqrt(n)

z for 95% confidence interval is 1.96

or 3 = 1.96 * 12 / sqrt(n)

Solving this, n = 61.46

We take the higher interger so that standard error is lower than 3 and not higher

N= 62

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