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Article: A simple and logical alternative for making PERT time estimates

TitleA simple and logical alternative for making PERT time estimates
Authors
Issue Date1996
PublisherTaylor & Francis Inc. The Journal's web site is located at http://www.tandf.co.uk/journals/titles/0740817x.asp
Citation
IIE Transactions (Institute Of Industrial Engineers), 1996, v. 28 n. 3, p. 183-192 How to Cite?
AbstractThe two standard steps for estimating PERT times are: Step 1, estimate a, in, and b; and Step 2, use the 'classical' formulae μ = (a + 4m + b)/6 and σ = (b -a)/6. We review the shortcomings of the textbook definitions of a, m and b; we also review the inconsistency of Step 1 with the literature on probability elicitation. A 5- or 7-fractile alternative is then proposed and justified for Step 1. Next, we develop simple but very accurate formulae for computing μ and σ with the fractiles estimated in our Step 1. For contrast, we also show that the classical PERT formulae are very inaccurate, even for the very restricted subset of beta distributions for which the formulae are supposedly applicable. Our overall purpose is to combine earlier findings with some new results to argue that: (i) the classical PERT formulae are both illogical and inaccurate, so we should not continue to teach and use them; and (ii) simple and more logical alternatives are available. © 1996 "IIE".
Persistent Identifierhttp://hdl.handle.net/10722/177847
ISSN
2015 Impact Factor: 1.463
2015 SCImago Journal Rankings: 1.293
References

 

DC FieldValueLanguage
dc.contributor.authorLau, AHLen_US
dc.contributor.authorLau, HSen_US
dc.contributor.authorZhang, Ven_US
dc.date.accessioned2012-12-19T09:40:33Z-
dc.date.available2012-12-19T09:40:33Z-
dc.date.issued1996en_US
dc.identifier.citationIIE Transactions (Institute Of Industrial Engineers), 1996, v. 28 n. 3, p. 183-192en_US
dc.identifier.issn0740-817Xen_US
dc.identifier.urihttp://hdl.handle.net/10722/177847-
dc.description.abstractThe two standard steps for estimating PERT times are: Step 1, estimate a, in, and b; and Step 2, use the 'classical' formulae μ = (a + 4m + b)/6 and σ = (b -a)/6. We review the shortcomings of the textbook definitions of a, m and b; we also review the inconsistency of Step 1 with the literature on probability elicitation. A 5- or 7-fractile alternative is then proposed and justified for Step 1. Next, we develop simple but very accurate formulae for computing μ and σ with the fractiles estimated in our Step 1. For contrast, we also show that the classical PERT formulae are very inaccurate, even for the very restricted subset of beta distributions for which the formulae are supposedly applicable. Our overall purpose is to combine earlier findings with some new results to argue that: (i) the classical PERT formulae are both illogical and inaccurate, so we should not continue to teach and use them; and (ii) simple and more logical alternatives are available. © 1996 "IIE".en_US
dc.languageengen_US
dc.publisherTaylor & Francis Inc. The Journal's web site is located at http://www.tandf.co.uk/journals/titles/0740817x.aspen_US
dc.relation.ispartofIIE Transactions (Institute of Industrial Engineers)en_US
dc.titleA simple and logical alternative for making PERT time estimatesen_US
dc.typeArticleen_US
dc.identifier.emailLau, AHL: ahlau@business.hku.hken_US
dc.identifier.authorityLau, AHL=rp01072en_US
dc.description.naturelink_to_subscribed_fulltexten_US
dc.identifier.doi10.1080/07408179608966265-
dc.identifier.scopuseid_2-s2.0-0030108497en_US
dc.relation.referenceshttp://www.scopus.com/mlt/select.url?eid=2-s2.0-0030108497&selection=ref&src=s&origin=recordpageen_US
dc.identifier.volume28en_US
dc.identifier.issue3en_US
dc.identifier.spage183en_US
dc.identifier.epage192en_US
dc.publisher.placeUnited Statesen_US
dc.identifier.scopusauthoridLau, AHL=7202626080en_US
dc.identifier.scopusauthoridLau, HS=7201497264en_US
dc.identifier.scopusauthoridZhang, V=14040949600en_US

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