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47 people found this helpful

ByRobert E. Welcyngon November 19, 2009

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".

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".

41 people found this helpful

ByYannison March 11, 2008

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...).

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...).

ByYannison March 11, 2008

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...).

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...).

ByJames Parlieron February 7, 2008

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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ByRobert E. Welcyngon November 19, 2009

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".

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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ByArchie Wilson Bullingtonon November 2, 2006

This book is an excellent introduction to the field of probability. It does not go into higher level mathematical theory, but presents the subject in easy to understand language and sticks to areas of practical application.

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ByNoDumbNameon March 20, 2014

I agree with the other reviews about the errors in the book. Also, the book does not provide any exercises, and without practice it is very difficult, if not impossible, to concur math.

Nevertheless, the book is very well written, and the examples provided are clear and easy to understand. The author clearly put some effort into making the subject matter interesting.

Nevertheless, the book is very well written, and the examples provided are clear and easy to understand. The author clearly put some effort into making the subject matter interesting.

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BySteven L. Milleron May 28, 2008

"Probability for Dummies" is an excellent book for students who are new to the subject of probability. It is easy to read, witty and very informative. This book would also serve as a fine review for students with previous experience in probability and statistics as well, for it deals with subject matter relative to both (in fact, the author makes references to another of her books, "Statistics for Dummies"). Highly recommended!

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Byjshatzon May 25, 2013

Very user friendly and comfortable to read. The book is giving me a clear understanding of probability which I always had trouble with and will need to pass for my undergraduate bachelor's degree program.

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ByAmazon Customeron April 8, 2016

This book is GOLD! I am two weeks away from my second exam for my Probability Theory class (400 lvl university course). Because I had no prior knowledge on probability (I probably knew just as much as a 6th grader would) I kept falling behind. The example that my course textbook gives were WAY too advanced for me to actually learn anything. The reading in my textbook is way too dry to actually 'read'. My professor assumes prior knowledge on the topic so he flies over the basics and I ended up really falling behind. I did grasp some concepts while grudgingly solving assigned problems along with the solution manual but I never fully understood what I was doing.

Then I found this book today. IT IS AMAZING!!! I wish I had this book since the beginning and I think would have been able to keep up with my class. It explains the material very efficiently while avoiding complex mathematical notations, which is the main reason I love this book so much.

This book does not provide many examples/practice problems for you to solve on your own, but it does provide sufficient amount in order to understand the concepts explained. While just reading the book is obviously not sufficient to pass my 400 lvl probability class, it is a great compliment to my dry textbook.

Then I found this book today. IT IS AMAZING!!! I wish I had this book since the beginning and I think would have been able to keep up with my class. It explains the material very efficiently while avoiding complex mathematical notations, which is the main reason I love this book so much.

This book does not provide many examples/practice problems for you to solve on your own, but it does provide sufficient amount in order to understand the concepts explained. While just reading the book is obviously not sufficient to pass my 400 lvl probability class, it is a great compliment to my dry textbook.

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ByAtill55on February 17, 2016

This book is not for the inexperienced! I would not recommend buying it if you consider yourself to be a "dummy" in the field of probability.

Ms. Rumsey begins the book with plenty of casual anecdotes about applying probability in everyday life. However, the text quickly becomes very dense with little practical application intertwined with the theory. The last third of the book ends up being rather repetitive and even more dense than the earlier parts.

The totality of this book is a collection of strong theory in probability. However, it was a slow and challenging read, that I was glad to be finished with.

Note*

- I took multiple undergraduate probability courses at a Big 10 university PRIOR to reading this book. In all of my classes, I received A's. I intended to use this book as a refresher, and found it substantially more difficult to follow than my coursework.

Ms. Rumsey begins the book with plenty of casual anecdotes about applying probability in everyday life. However, the text quickly becomes very dense with little practical application intertwined with the theory. The last third of the book ends up being rather repetitive and even more dense than the earlier parts.

The totality of this book is a collection of strong theory in probability. However, it was a slow and challenging read, that I was glad to be finished with.

Note*

- I took multiple undergraduate probability courses at a Big 10 university PRIOR to reading this book. In all of my classes, I received A's. I intended to use this book as a refresher, and found it substantially more difficult to follow than my coursework.

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ByAbacuson February 16, 2010

Overall, this is a good book that serves well as a very thorough introduction to probabilities and statistical distributions. The author covers a very large domain that is probably equivalent to at least one semester course at the college level. I was surprised at the number and complexity of statistical distributions covered and at the depth of the combination and permutation topics applications.

This book should fulfill the knowledge needs of most people needing such an introduction to probabilities. The author provides all the formulas and tools needed to deal with not only basic but also fairly advanced stuff (with statistical distributions the learning curve accelerates into the advanced domain readily).

As mentioned in the title of this review, the author is not as accurate as she should have been. Some errors are permissible. Other errors are less so. Among the permissible errors are the author's treatment of the famous birthday problems. I won't bore you with the technicalities others have already well specified. In any case, the author comes up with an elegant estimate of a solution to the birthday problem. But, it is not 100% accurate. The only error the author did here is to forget to mention this was an estimation and not an accurate solution. There are many well accepted estimations to the birthday problem and the author's is as reasonably accurate as any others (I have partly checked that).

Among the errors that are less permissible, right at the beginning of the book the author completely messes up what odds are. She states that odds is the inverse of a probability. It is not. The odds is either the probability of winning divided by the probability of losing (called Odds on) or the reverse (Odds against). Later in the book, she also bungles the Z distribution probability density function. Those are material errors that discredit the author.

So, there you have it. This is a good book overall, but watch out for some errors. If you study statistical distributions in depth I would double check every pmf or pdf formulas with another source such as Wikipedia.

If you want to build your mathematical foundation I also strongly recommend Forgotten Algebra,Forgotten Calculus, and Forgotten Statistics: A Refresher Course with Applications to Economics and Business. Those books were somewhat more accessible than this one (shorter on theory, more exercises, and superior in quality).

This book should fulfill the knowledge needs of most people needing such an introduction to probabilities. The author provides all the formulas and tools needed to deal with not only basic but also fairly advanced stuff (with statistical distributions the learning curve accelerates into the advanced domain readily).

As mentioned in the title of this review, the author is not as accurate as she should have been. Some errors are permissible. Other errors are less so. Among the permissible errors are the author's treatment of the famous birthday problems. I won't bore you with the technicalities others have already well specified. In any case, the author comes up with an elegant estimate of a solution to the birthday problem. But, it is not 100% accurate. The only error the author did here is to forget to mention this was an estimation and not an accurate solution. There are many well accepted estimations to the birthday problem and the author's is as reasonably accurate as any others (I have partly checked that).

Among the errors that are less permissible, right at the beginning of the book the author completely messes up what odds are. She states that odds is the inverse of a probability. It is not. The odds is either the probability of winning divided by the probability of losing (called Odds on) or the reverse (Odds against). Later in the book, she also bungles the Z distribution probability density function. Those are material errors that discredit the author.

So, there you have it. This is a good book overall, but watch out for some errors. If you study statistical distributions in depth I would double check every pmf or pdf formulas with another source such as Wikipedia.

If you want to build your mathematical foundation I also strongly recommend Forgotten Algebra,Forgotten Calculus, and Forgotten Statistics: A Refresher Course with Applications to Economics and Business. Those books were somewhat more accessible than this one (shorter on theory, more exercises, and superior in quality).

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