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# Using Crystal Ball for Simple Analysis

4 replies [Last post]
Martin Selley
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Joined: 4 Mar 2006
Posts: 7

Looking for 'Idiots Guide' type assistance with Crystal Ball (Oracle) as Excel Supplement.

Have never used the Software, downloaded yesterday, and I have to come up with some P10, & 90 Durations for a Manufacturing/testing/shipping schedule due to be received next week.

Would use the Manufacturers Schedule Durations as P50 Input.

Can some one please advise how then to get the P10 & P90 dates.

Thanks.

## Replies

Rafael Davila
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Joined: 1 Mar 2004
Posts: 4784

Be aware that Probability of Occurrence (probability distribution) is not the same as Cumulative Probability (probability of success).

If an event has a 90% probability of occurrence then the sum of all remaining events probabilities of occurrence is limited to 10% as the summ of all probabilities of occurrence by definition equals 1.00 or 100%.

http://www.mcgrawhill.ca/college/olcsupport/siklos4/tables/table%2013.6.pdf

In the above example the probability of occurrence corresponding to 20% corresponds equally to 3 ranges while the cumulative probability (usually known as probability of success) corresponds to a single range in between the first two.

Common sense tells me P10, P50 and P90 refers to Cumulative Probability (probability of success) and not to Probability of Occurrence (probability distribution).

Martin Selley
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Joined: 4 Mar 2006
Posts: 7

P10, P50, P90 percentages probability of occurance

P10 is a 10 percent chance of occurance, P50 is a 50 percent chance and P90 is a 90 percent chance of occurance. Used in forecasting of business results

Rafael Davila
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Joined: 1 Mar 2004
Posts: 4784

P10, P50, and P90 I believe refers to points in the Cumulative Probability Curve.

For specifics on the software look for the manual,

http://www.biztech.stevens-tech.edu/jkeating/BT%20223/Crystal%20Ball/200...

make a search on the PDF for Cumulative

Best regards,

Rafael

Mike Testro
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Joined: 14 Dec 2005
Posts: 4395

Hi Martin

Sorry Ican't help but you seem to be the person to tell Rafael and I what does P10 P50 and P90 mean?

Best regards

Mike Testro