# Thread: Binomial Distribution in Excel

1. ## Binomial Distribution in Excel

7. An emergency room administrator wants to know the proportion of emergency room patients who spend more than one hour waiting to be seen. He has records that for each patient show the time of arrival at the emergency room and the time when seen by a member of the medical staff. He selects a random sample of 50 records and discovers that 14 patients waited more than one hour to be seen.
a. What is the probability that the true proportion of persons spending more than one hour is 20% or less?

What i have concluded is first finding the probability of the patients waiting for an hour which is: 0.28

then i get stuck i dont even know what would go in where when it comes to this function

BinomDist (number_s, trials, probability_s,cumulative)
I believe it is (X, 50,0.28,False) but what would x be how would i find that?

thank you for the help!

2. ## Re: Binomial Distribution in Excel

Hi xdayita,

im not using excel so i had to look it up...
http://office.microsoft.com/en-gb/ex...005209005.aspx

I believe it is (X, 50,0.28,False) but what would x be how would i find that?
X is 14 (Successes == Waited for more than 1 hour), 50 is the whole sum of values taken which you got right, 0.28 is the probability to wait more than 1 hour==translates to a 28 % probability to wait more than 1 hour).

You may also use R - its free and helpful in statistics:
Code:
``binom.test(14,50,1/2)``
Where 14==Waited for more than 1 hour
Where 50==is the whole sum of values taken
Where 1/2==Possible outcomes == Wait at least or less 1 hour / Wait more than 1 hour

R-Output is:
Exact binomial test

data: 14 and 50
number of successes = 14, number
of trials = 50, p-value = 0.002602
alternative hypothesis: true probability of success is not equal to 0.5
95 percent confidence interval:
0.1623106 0.4249054
sample estimates:
probability of success
0.28

Hope this helps.

Sebastian

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