how to use excel to find answer: A local indian restaurant advertises home deliv

Question

how to use excel to find answer: A local indian restaurant advertises home delivery times of 30 minutes. To monitor effectiveness of this promise the restaurant manager monitors the time that the order was received and the time of delivery. Based upon historical data the average time for delivery is 30 minutes with a standard deviation of 5 minutes. After a series of complaints from customers regarding this promise the manager decided to analyze the last 50 orders which resulted in an average of 32 minutes. Conduct an appropriate test at a significance level of 5%. should the manager be concerned.

Explanation / Answer

Data:     

n = 50    

= 30    

s = 5    

x-bar = 32    

Hypotheses:     

Ho: 30    

Ha: > 30    

Decision Rule:     

= 0.05    

Critical z- score = 1.644853627    

Reject Ho if z > 1.644853627    

Test Statistic:     

SE = s/n = 5/50 = 0.707106781   

z = (x-bar - )/SE = (32 - 30)/0.707106781186547 = 2.828427125   

p- value = 0.002338867    

Decision (in terms of the hypotheses):     

Since 2.828427125 > 1.644853627 we reject Ho and accept Ha

Conclusion (in terms of the problem):   

There is evidence that the mean delivery time is more than 30 minutes. The manager should be concerned.

(You can only find the p- value for the z- score using Excel. Or you will have to use an excel add-in such as PHStat or MegaStat to conduct the hypothesis test).

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