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Title: Waltzing With Bears: Managing Risk on Software Projects by Tom Demarco, Timothy Lister ISBN: 0-932633-60-9 Publisher: Dorset House Pub. Date: March, 2003 Format: Paperback Volumes: 1 List Price(USD): $27.95 |
Average Customer Rating: 4.6 (15 reviews)
Rating: 1
Summary: Getting Back to Basics
Comment: It never ceases to amaze me how easily impressed the masses are by well-expressed views expounded by eminent personalities with a proven track record for impressing. So strong is this effect that even when the views expressed are fundamentally flawed one rarely sees the offenders brought to account. Here, with 'Waltzing With Bears' we have a prime example: a book crammed with seemingly good advice on how to evaluate risk but which commits the cardinal sin of applying frequentist probability theory to model epistemic uncertainty. As a result we have yet another pair of consultants jumping on the bandwagon and promoting an aleatory method (Monte Carlo Simulation) without any regard for the second order uncertainties that bedevil software development projects. Why is this important? Because all the results you get will be wrong; very impressive but useless. I don't know about you, but I think that this is a serious drawback.
I believe it behoves renowned experts to do their homework and get the basics right before they pollute the education system with their half-baked 'wisdom'. Do yourself a favour, ignore what the book says about risk analysis and go and by a good book on Bayesian Methods and Decision Theory. You don't have to take my word for this, just type in 'epistemic uncertainty and Monte Carlo' into your Internet search engine and take it from there. In the meantime, here are some background notes to help explain my remarks:
There are two types of uncertainty: epistemic and aleatory.
As the name suggests, epistemic uncertainty results from gaps in knowledge. For example, one may be uncertain of an outcome because one has never used a particular technology before. Such uncertainty is essentially a state of mind and hence subjective.
Aleatory uncertainty results from variability that is intrinsic to the behaviour of some systems (alea is the Latin for die). For example, I can be confident regarding the long term frequency of throwing sixes but I remain uncertain of the outcome of any given throw of a dice. This uncertainty can be objectively determined.
There are two branches of probability theory: Frequentist and Bayesian.
Frequentist probability theory is used to analyse systems that are subject to aleatory uncertainty.
Bayesian probability theory is used to analyse epistemic uncertainty.
For most risk assessments a Project Manager has to undertake, there is both epistemic and aleatory uncertainty but epistemic uncertainty is always significant due to the novelty of the situation under assessment.
Standard Monte Carlo Simulation uses frequentist probability theory to analyse risk.
When Monte Carlo is used to model schedule risk, the schedule uncertainties are being treated as if they are aleatory, even though they are predominantly epistemic. This is now considered to be unrealistic and is known to give incorrect results. The main problem is that the second order uncertainties are often too large to be ignored, i.e. the required shape for the chosen probability distribution curves is more important than the tool vendors would have you believe and yet they are usually imprecisely known.
Using standard Monte Carlo to analyse schedule risk also requires unrealistic assumptions to be made regarding the correlations between the probabilities for the individual outcomes, e.g. that there are no correlations or that they are all of the same nature. In practice, there are correlations to be considered when analysising schedule risk and they are of both a positive and negative nature.
As a result of the above drawbacks many expert authorities are warning against the use of Monte Carlo Simulation where the historical data upon which the analysis is premised is incomplete. For example, its use in ecological and economic models is now controversial (see the World Congress on Risk website).
In software development there is a growing appreciation of the importance of Bayesian Methods in analysing problems in software quality assurance.
Bayesian methods are appropriate in situations where there are gaps in information (i.e. where there is epistemic uncertainty). They involve the creation of Bayesian Belief Networks (BBNs) to model causal relationships. Data is fed into the model to enable the probability of specified outcomes to be calculated given the current body of knowledge.
Even more interesting, Bayes Theorem can be used to assess the likelihood that pre-conditions exist in the light of outcomes becoming known.
BBNs can be used in any situation where one is trying to calculate the likelihood of an outcome, or an unknown situation, when there is only limited information. It is useful in Decision Theory when a risk-based decision is required in the face of epistemic uncertainty.
Rating: 5
Summary: Super book on the Critical Subject of Risk Management
Comment: What an excellent book, but then what would one expect from Tom DeMarco and Tim Lister, and Dorset House? As well as being an excellent introduction to an extremely vital subject in this day and age, "Waltzing with Bears" provides some practical tips not only on how to do Risk Management, but also regarding how to overcome some of the factors in corporate culture that actively or passively suppress the application of Risk Management (e.g., the "can-do" attitude).
DeMarco and Lister have structured this book logically, beginning with "Why" and "Why Not", progressing through "How" and "How Much", and concluding with a brief "Whether or Not". The chapter on Core Risks of software projects is priceless. The authors provide instruction on how to graphically show the uncertainty that must be managed, and provide a link to a freeware RISKOLOGY tool that will assist those engaged in Risk Management.
Having spent several years in QA and Process Engineering supporting Risk Management, I can only say that I wish I'd had this book several years ago. But I have it now, and am better prepared for future efforts.
Thanks again, Tom and Tim. By the way, I love the cover.
Rating: 4
Summary: Useful for managers of medium to large groups of people
Comment: There are a ton of wonderful anecdotes and motivational examples for doing risk management. Also, he takes a very pragmatic approach towards what's actually possible in different corporate climates. Rather than only telling you what right thing to do is, he helps you decide what the appropriate thing is.
The explanation of the relationship between risk and benefit analysis was both insightful and seemed like it would be useful. It provides a pragmatic framework for a lot of what are considered 'good engineering practices', such as incremental deliverables that can be measured and verified in meaningful ways.
The only downside is that it's very difficult to understand how to take advantage of some of the frameworks he provides without being in a management position already. Individual contributors won't get a lot out of this.
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Title: Slack : Getting Past Burnout, Busywork, and the Myth of Total Efficiency by TOM DEMARCO ISBN: 0767907698 Publisher: Broadway Pub. Date: 09 April, 2002 List Price(USD): $14.95 |
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Title: Peopleware : Productive Projects and Teams, 2nd Ed. by Tom Demarco, Timothy Lister, Timothy R. Lister ISBN: 0932633439 Publisher: Dorset House Pub. Date: 01 February, 1999 List Price(USD): $33.95 |
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Title: Facts and Fallacies of Software Engineering by Robert L. Glass ISBN: 0321117425 Publisher: Addison-Wesley Pub Co Pub. Date: 28 October, 2002 List Price(USD): $29.99 |
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Title: Professional Software Development: Shorter Schedules, Higher Quality Products, More Successful Projects, Enhanced Careers by Steve McConnell ISBN: 0321193679 Publisher: Addison-Wesley Pub Co Pub. Date: 30 June, 2003 List Price(USD): $29.99 |
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Title: The Deadline: A Novel About Project Management by Tom Demarco ISBN: 0932633390 Publisher: Dorset House Pub. Date: July, 1997 List Price(USD): $24.95 |
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