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hackman20... hackman20...
 
M$2 February 26, 2009 12:44 AM

What formula to use for this Statistics problem?

I'm trying to solve a Statistics problem.

A local university reports that 3% of their students take their general education courses on a pass/fail basis. Assume that fifty students are registered for a general education course What is the probability that less than four are registered on a pass/fail basis?

I'm not sure what formula to use on this type of problem.

Can anyone tell me what formula I would be using for this problem? Thanks.
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pmacdon1 pmacdon1
 
 February 26, 2009 01:35 AM
Please note I did not write this answer, I just copied it word from word from my source. Another person had the exact same question:

I think this calls for a sampling distribution of proportion. Your sample proportion of interest is <=.06 (less than 4 out of 50 students).
P=.03 (population proportion)
p=.06 (sample proportion of interest)
n=50 (sample size)

z= (p-P)/SQRT(P(1-P)/n)

z= (0.06 - 0.03) / SQRT(0.03(1-0.03)/50)

Solve that z, look it up on a normal distribution table. Your answer is the area to the left of it.
Source(s):
http://talkstats.com/showthread.php?t=7381

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hackman200... hackman200...
 
February 26, 2009 02:34 AM
Actually that answer is wrong. The person that posted that thread is actually me LOL.

I think they were onto a total different aspect with that formula.

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pmacdon1 pmacdon1
 
February 26, 2009 02:39 AM
It seems to work for me, I worked out a z value of 1.244 which gave me the answer as a probability of ~90%

Is that not correct?

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hackman200... hackman200...
 
February 26, 2009 02:49 AM
The homework is reporting the answer as not 0.8925 (is this the answer of about 90% you got?).

I don't think this is related to z-score since the sheet we have only goes up to .5000 on both sides. I had to look for another one on Google.

I think there is a different way he wants us to do this.

The answer has to be to four decimal places by the way.

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hackman200... hackman200...
 
February 27, 2009 05:50 PM
Okay, maybe that was right. I was looking at the wrong type of table. Mine only went up to .5000, but it CAN go up to 1.000.

Statistics sucks.

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kenman345 kenman345
 
February 28, 2009 12:31 AM
i actually believe that is wrong. I check it out with my teacher and this is what we came up with:
i got .77649903 as my answer.

They are independent events and so you multiply your results

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pmacdon1 pmacdon1
 
February 28, 2009 03:39 AM
According to hackman, his homework says that 89.25% is the correct answer.

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Other Answers (2)

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elly2222 elly2222
 
February 26, 2009 07:18 AM
Are you supposed to assume normal distribution?

If so, try this:
http://en.wikipedia.org/wiki/Cumulative_distribution_function

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hackman200... hackman200...
 
February 26, 2009 02:46 PM
No, this is the reason I don't think it is a normal distribution. We just started normal distribution yesterday and we have had this homework for a while. It is over Chapter 5, normal distribution is chapter 6 homework. In chapter 5, we covered:

Random Variables
Discrete Probability Distributions
Expected Value and Variance
Binomial Probability Distribution
Poisson Probability Distribution
Hypergeometric Probability Distribution

I think it is a Binomial Probability Distribution, but I don't know how to calculate it. Hence why I want the formula.

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karj karj
 
February 26, 2009 06:27 PM
hi hackman2007
There is a solution for a similar kind of problem from some website
Hope you can figure out the formula.If not I will help you more if I can

A local university reports that 20% of their students take their general education courses on a pass/fail basis. Assume that fifteen students are registered for a general education course What is the probability that less than two are registered on a pass/fail basis?
Answer:0.5491
Hope it is helpful
Source(s):
http://202.115.21.138/wlxt/ncourse/swttx/web/08/swf/xtj04.swf


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