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About ronny fisher
Expertise
general questions on probability and statistics. please do not send intro prob/stat homework questions.

Experience
have taught probability and stats for 25 years

Education/Credentials
ba in math, phd in stats

Past/Present Clients
federal government, state AG, start-up pharma companies, engineering consulting firms, academic researchers (the list goes on).

 
   

You are here:  Experts > Science > Mathematics > Probability & Statistics > Minimum Sample

Probability & Statistics - Minimum Sample


Expert: ronny fisher - 7/25/2009

Question
Hello, If i have a very large bucket of several thousand balls. All I know is that almost all the balls are black and a small percentage are red. If i take out a ball one at a time and note the color. What is the minimum number of balls i need to take out to have an almost certain accuracy of the ratio of black to red balls ?
Im looking for an answer will sound something like: you will need X number of red balls to be 90% sure of the ratio and Y number of red balls to be 99% sure  etc.
Thanks !

Answer
mike -

the sort of answer you want is not clear. in particular, the sentence you wrote:

"Im looking for an answer will sound something like: you will need X number of red balls to be 90% sure of the ratio and Y number of red balls to be 99% sure  etc."

seem garbled.

if you rephrase the question a bit more carefully, i might get a better grasp of what you are looking for.

ronny

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