Awaitress makes $2.15 per hour, plus tips. she estimates that her tips for a shift will total 20% of the total of her customers' receipts, r. if she works a 10 hour shift, which expression represents her expected pay for that shift? $21.50 + .2r $2.15 + .2r $2.35r $23.50r

At 95% confidence interval, the z score is 1.96. Using the formula:

Confidence Interval = x ± z s / sqrt (n)

where x is the average time served, s is standard deviation and n is number of samples

Confidence interval = 7.5 ± (1.96 * 3) / sqrt (400)

Confidence interval = 7.5 ± 0.294

Confidence interval = 7.206 to 7.794