Homework SourseChicken Delight claims that 91 percent of its orders are del
Chicken Delight claims that 91 percent of its orders are delivered within 10 minutes of the time the order is placed. A sample of 90 orders revealed that 77 were delivered within the promised time. At the .025 significance level, can we conclude that less than 91 percent of the orders are delivered in less than 10 minutes?
Compute the value of the test statistic. (Negative amount should be indicated by a minus sign.Round sample proportion to 2 decimal places. Round your answer to 2 decimal places.)
| Chicken Delight claims that 91 percent of its orders are delivered within 10 minutes of the time the order is placed. A sample of 90 orders revealed that 77 were delivered within the promised time. At the .025 significance level, can we conclude that less than 91 percent of the orders are delivered in less than 10 minutes? |
Solution
(a) Given a=0.025, the critical value is Z(0.025) =-1.96 (from standad normal table)
Reject Ho if z <-1.96
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(b) test statistic is
Z=(phat-p)/sqrt(p*(1-p)/n)
=(70/90-0.91)/sqrt(0.91*(1-0.91)/90)
=-4.38
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(c)Reject H0
