A coffee shop claims that it takes 115 seconds, on average, to serve their customers coffee through the drive-thru. Lucy, a statistics student, decides to test this claim. She randomly selects 15 orders and records the wait time it took for the customer to receive their coffee. Here are the times (in seconds). 85 122 135 100 153 153 116 99 65 130 175 113 188 142 134 (a) Why is it important that Lucy selects a random sample of orders? (b) Lucy wants to make a confidence interval to estimate the true mean wait time. Explain thoroughly why Lucy has or has not satisfied the “normal” condition for constructing a confidence interval. (c) The 95% confidence interval for the true mean wait time is (109.1, 145.6) seconds. Does the interval provide convincing evidence that the coffee shop is lying about their claim? Explain.
A coffee shop claims that it takes 115 seconds, on average, to serve their customers coffee
through the drive-thru. Lucy, a statistics student, decides to test this claim. She randomly
selects 15 orders and records the wait time it took for the customer to receive their coffee.
Here are the times (in seconds).
85 122 135 100 153
153 116 99 65 130
175 113 188 142 134
(a) Why is it important that Lucy selects a random sample of orders?
(b) Lucy wants to make a confidence
thoroughly why Lucy has or has not satisfied the “normal” condition for constructing a
confidence interval.
(c) The 95% confidence interval for the true mean wait time is (109.1, 145.6) seconds. Does the
interval provide convincing evidence that the coffee shop is lying about their claim? Explain.
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