Probability

[Dennis]

I am working on a question for a statistics class. We are supposed to find
Excel program to answer the following question.

The probability that a worker is absent from work more than 2 times a year
is 0.4. There are 200 workers in the sample. What is the probability that
more than 7 workers will be absent more than 2 times per year. The answer is
..741044. Can anyone help me find the function that will perform this
operation?

 

[David Biddulph]

Are you sure that it didn't ask for the probability of more than *75*,
rather than more than 7?

 

[Dennis]

You are right, it is 75.
--
Dennis

Are you sure that it didn't ask for the probability of more than *75*,
rather than more than 7?

 

[notloiseweiss]

Dennis,

I believe the way to solve the problem is to calculate 1 - (probability that
7 or fewer people miss 2 days of work) = 1 - P(7 people miss 2 days of work)
- P(6 people miss 2 days of work) - P(5 people miss 2 days of work) ... - P(0
people miss 2 days of work).

This can likely all be calculated using the binomial function in excel...
BINOMDIST

 

[David Biddulph]

Good! It's always comforting if given the answer you can work out what the
question is.

I wondered whether your lecturer may have hoped that you use something like
the Central Limit Theorem approximation to the Binomial Distribution (if
you've covered that in your syllabus), but that doesn't come to quite the
answer you gave. You can let Excel do it the crude number-crunching way,
and work out the probability that the number absent is zero, then the
probability for 1, then for 2, etc. You can add up the probabilities for N
= 0 to 200 and confirm that you've got your formula right by seeing that
these add up to 1. You can add up p(N) for N = 0 to 75, and that will give
the probability that the number is 75 or fewer; subtract that from 1 and
you've got the number you're after.

If you want, you can let Excel plot the crude number crunching value for the
cumulative distribution and also plot the Central Limit Theorem
approximation.

 

[Martin P]

=1-BINOMDIST(75,200,0.4,TRUE)

 

[Dennis]

Thanks Martin!!!!
--
Dennis

=1-BINOMDIST(75,200,0.4,TRUE)