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Topic: Help with probability&stat problem
Replies: 47   Last Post: Jun 16, 2007 4:32 AM

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 tutorny Posts: 39 Registered: 1/28/06
Help with probability&stat problem
Posted: Jun 11, 2007 12:27 PM

I am looking at solving the following problem:

Past records show that at a given college 20% of the students who
began as psychology majors either changed their major or dropped out
the school. An incoming class has 110
beginning psychology majors. What is the probability that as many as
30 of these students leave the psychology program?

I think that I can solve it using the normal approximation to the
binomial probability distribution, as follows:

n =110, p = 0.20
mean = u = np = 110*0.20 = 22
standard deviation = s.d. = (n*p*q)^.5 = (110*.20*.80)^.5 = 4.1952

We want P(x <=30)

When x = 30, z = (x - u)/s.d = (30 - 22)/4.1952 = 1.9069

So, we want P(z<=1.9069) = 0.9717

So, the answer is 97.17 percent.

Can you tell me if you see anything wrong with this answer, or the way
that I solved this problem? Any help is greatly appreciated.

Thanks!

Date Subject Author
6/11/07 tutorny
6/11/07 briggs@encompasserve.org
6/11/07 tutorny
6/11/07 Randy Poe
6/11/07 tutorny
6/11/07 Bruce Weaver
6/11/07 tutorny
6/11/07 Bruce Weaver
6/11/07 C6L1V@shaw.ca
6/11/07 Randy Poe
6/11/07 tutorny
6/11/07 Nick
6/11/07 Jack Tomsky
6/11/07 Luis A. Afonso
6/11/07 Jack Tomsky
6/11/07 Luis A. Afonso
6/11/07 Jack Tomsky
6/12/07 Luis A. Afonso
6/12/07 Jack Tomsky
6/12/07 Luis A. Afonso
6/12/07 Jack Tomsky
6/12/07 Luis A. Afonso
6/13/07 Jack Tomsky
6/13/07 Luis A. Afonso
6/13/07 Anon.
6/13/07 Jack Tomsky
6/13/07 Jack Tomsky
6/13/07 Luis A. Afonso
6/13/07 Jack Tomsky
6/13/07 Anon.
6/13/07 Luis A. Afonso
6/13/07 Jack Tomsky
6/13/07 Jack Tomsky
6/13/07 Anon.
6/13/07 Luis A. Afonso
6/13/07 Jack Tomsky
6/13/07 Luis A. Afonso
6/13/07 Jack Tomsky
6/14/07 Luis A. Afonso
6/14/07 Luis A. Afonso
6/14/07 Jack Tomsky
6/14/07 Luis A. Afonso
6/15/07 Luis A. Afonso
6/15/07 Jack Tomsky
6/15/07 Luis A. Afonso
6/15/07 Jack Tomsky
6/15/07 Luis A. Afonso
6/16/07 Luis A. Afonso