26 of 28 people found the following review helpful:
3.0 out of 5 stars
Not bad, but really for dummies!, March 11, 2008
This review is from: Probability For Dummies (Paperback)
I mostly enjoyed this book, and I now feel more comfortable with certain concepts that I had always tended to ignore. Gone are the days when, upon hearing the slightest complex-sounding word on probabilities, I would automatically revert to the ostrich technique. This book definitely helps you face such little words in probabilities and statistics, and it truly gives you confidence in doing so.
Yet, important as the above may be if you do not intend to use a lot of probs theory, that's about all this book does for you... Evidently, that's just not enough for someone you wants to start using probabilities. And my intuition is that, if you want to read a book on probabilities, that's because you want to use them.
Plainly, this book is a little bit too easy. I do not consider myself to be anything like beyond the mean of a normal distribution of IQ scores. And yet I constantly thought that I needed a more of two things, and less of another.
1) I needed more exercises: if one buys this, it is probably because one wants to start using probs, and exercises are the best way to start learning; and
2) I needed more text on applications: if one buys this, it is probably because they want to see how props are used in real-world and/or academic contexts.
3) Conversely, I thought I needed a little bit less of repetition: every chapter need not read as a self-standing piece, which recaps everything and then adds just a tiny little bit more. People tend to read books from the beginning to the end; they do not just open this king of books at a random page and start reading... In my experience, repetition reaches a point where it starts having decreasing returns: instead of consolidating knowledge, it confuses (he or she starts wondering what is new about the new page or chapter) and bores the reader.
So, do buy this book if you're revising for exams, or if you really know nothing about probabilties. But if you either care to really learn about probabilities, or you already know a little bit about them, then try another book that can get you further (lots of books on finite maths take you further than this one in just one chapter...).
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15 of 16 people found the following review helpful:
4.0 out of 5 stars
Unacceptable Errors, November 19, 2009
This review is from: Probability For Dummies (Paperback)
I am revising my review of this book due to the seriousness of one particular error.
On page 126, the author, Deborah Rumsey, addresses "The Famous Birthday Problem." Basically, the problem asks, "Given n people in a group, what is the probability of at least two of them sharing a birthday?"
This problem and its correct solution are well known and can be found in numerous authoritative texts such as William Feller's "Probability Theory and Its Applications" and on the Internet as well.
At first blush, Rumsey's different from the traditional approach to this problem seemed clever to me. However, upon closer examination, her method turns out to be flawed.
For example, if there were four people in the group, the correct calculation for the probability that at least two of the four people share a birthday is:
1 - (365/365)(364/365)(363/365)(362/365)
According to Rumsey's method, however, the corresponding probability would be:
1 - (364/365)(364/365)(364/365)(364/365)(364/365)(364/365)
Rumsey's "solution" is not mathematically equivalent to the first (correct) solution, although, fortuitously, the calculated results are nearly the same (0.0163559 versus 0.0163262). This difference reveals a subtle error in the logic of Rumsey's approach to the problem.
I'm rating this book with a single star because I feel that an error of logic in a book that purports to teach probability is not acceptable. I enjoyed reading Probability For Dummies, but I am disappointed that an otherwise well written, entertaining, and useful book has been stained by a fundamental error in reasoning.
Other errors in the book are:
On page 9, both the definition and example of the term "odds" are incorrect. "Odds" is not the ratio of the denominator to the numerator of a probability, but rather the ratio of the probability of success for a given event to the probability of failure of that event. If the probability of a horse winning a race is 50%, the odds of the horse winning is 1 to 1, not 2 to 1 as the book states.
On page 169, the formula that defines the normal distribution is incorrect. The denominator of the exponent should be "twice sigma", not "sigma".
On page 170, the formula that defines the Z distribution is incorrect. The exponent "minus Z squared" should be "minus Z squared divided by two".
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25 of 29 people found the following review helpful:
3.0 out of 5 stars
A little skeptical, February 7, 2008
This review is from: Probability For Dummies (Paperback)
I was a little disappointed to see a mistake in the introduction, under discussion of odds. The claim made was that if a horse had a 50% chance of winning, the odds were 2 to 1. In fact the odds are 2 FOR 1 or 1 to 1. If a horse has a .50 probability of winning, it stands that it also has a .50 probability of losing. 0.50 = 0.50 therefore 1 TO 1. In a gambling setting, if someone paid you 2 to 1 odds on a .50 probablility event, they would go broke quickly. If they paid you 2 FOR 1 everyone would break even in the long run.
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