Hi,

I tried solving the following problem using figures from Minitab and Excel:
 

Calculate probability for the Pizza Delivery within 30 minutes if the process has a mean of 20 mins and Stdev of 3.5 and determine the penalty for probable late deliveries for 100,000 deliveries @ 200 INR.

I get a different penalty for left-tailed and right-tailed probability using Minitab (ref: spreadsheet attached).

 

• Is the difference in penalty due to rounding error, or am I missing something?
• Is there a function to calculate right-tailed probability in Excel? Is using 1-NORMDIST correct?
• In Excel's NORMDIST(x, mu, sigma, cumulative) function, what does "cumulative" mean?

Thanks,
Kashi

pizza-delivery.xls

Hi, 

 

• Yes, it is just a rounding off error that causes the difference. 
• The formula in excel uses normsdist and not normdist.