Actually, that should be "doubt about the given answer."
I concur with the other two observed responders but would like to emphasize
the issue that Mr. (Dr.?) Dunne raises, which is the inherent illogic of the
textbook answer. Although I am too far removed from such exercises to be
trustworthy, it seems to me that, if the probability of non-illness of the
noninoculated person is .4, the probability of non-illness in both _cannot_
be greater than .4. Some law of nature that I seem to recall states: p(a and
b) <= p(a). I shall be much obliged to the person who can show this to be
wrong. Or inapplicable to the present exercise.
Respectfully,
Michael
------------------------------
Date: Sat, 3 Sep 2005 18:07:37 -0400
From: "Alan E. Dunne" <[log in to unmask]>
Subject: Fw: doubt about exercise
----- Original Message -----=20
From: "Alan E. Dunne" <[log in to unmask]>
To: "Rodrigo Briceno" <[log in to unmask]>
Sent: Friday, September 02, 2005 6:27 PM
Subject: Re: doubt about exercise
> With Respect
>
>
> I thought the catch was that the inoculation reduces the chance of
> getting flu by 80%, or 0.48, so that the inoculated have a chance of
> getting si=
ck
of
> 0.12 not 0.2
>
> -but this gives me 0.528 + 0.048 + 0.072 =3D 0. 648
>
>
> Note the textbook answer gives a probability of boh employees not
being
> sick of 0.4048, more than, the 0.4 both Mr Briceno and I took as the
chance
> of the non-inoculated employee not being sick.
>
>
> Yours Sincerely,
> Alan E. Dunne
>
> ----- Original Message -----=20
> From: "Rodrigo Briceno" <[log in to unmask]>
> To: <[log in to unmask]>
> Sent: Tuesday, August 30, 2005 10:29 AM
> Subject: doubt about exercise
>
>
> Dear co-listers. I was solving some exercises on probability topics,
> bu=
t
> suddenly a doubt came to me when I tried to solve a problem.
>
>
>
> The problem says that: Suppose that the probability of being sick of
> fl=
u
> during an epidemic is 0.6. The past experience has showed that certain
serum
> is effective in 80% of the times to avoid a person being sick of flu,
> i=
f
the
> person is exposed to it. Two people, one inoculated and the other
> don't
are
> employees of a company. Suppose that they aren't in the same place,
> the=
y
are
> not in contact with the same people and they can't be infected between
each
> other. What is the probability that at least one of them is affected
> by
the
> flu?
>
>
>
>
>
> I make the following reasoning:
>
>
>
> Non-inoculated sick, inoculated non-sick: 0.6 X 0.8 =3D 0.48
>
> Non-Inoculated non-sick, inoculated sick: 0.4 X 0.2 =3D 0.08
>
> Both Sick: 0.6 X 0.2 =3D 0.12
>
>
>
> Answer: 0.68. I don't know if the procedure and reasoning are wrong,
> bu=
t
the
> textbook says that the answer (without explaing how they get it) is
0.5952.
>
> Can somebody provide me advice to this respect?
>
>
>
> Thanks for your kindly cooperation.
>
>
>
>
>
> _________________________________
>
> Rodrigo Brice=F1o
>
> Consultor
>
> Sanigest International
>
> San Jos=E9, Costa Rica
>
> Telf. (506) 291-1200, ext.118
>
> Fax. (506) 232-0830
>
> Cell (506) 357-4535
>
> www.sanigest.com
>
> Apdo. 23-2015 Zapote Costa Rica
>
> __________________________________
>
>
------------------------------
End of allstat Digest - 2 Sep 2005 to 3 Sep 2005 (#2005-217)
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