# Sample size calculation--population is known

#### bhardwajsaurabh

##### New Member
Okay, so the goal is to survey...

If you don't know the expect proportion you should take the worse case: Proportion=0.5
population=129,517
confidence level=0.95
MOE=0.05

sample size=385

This says that if you get the result that 0.5 (50%) of the sample prefer the green color.
The confidence interval will be 0.5±0.05 or 50% ± 5%.
1)Thanks a ton friend.what is the formula you used.

2)Also help me solve my one more query.

i have to upload a excel file with different fields to call the customer for survey.how can i prove that my survey is unbiased and random.

I upload the data of total number of repairs done in a week.please suggest,is there any way to prove the data is random like a run test for continuous data.

Also a very Happy New year in advance.!!

Thanks..

#### obh

##### Active Member
Hi Saurabh,

Just use the following link with:
confidence level=0.95
Proportion= 0.5
MOE=0.05
population=129,517

and you get the formula and corrected sample size of 384.

Usually, you plan a survey to get unbias results ...
What are your expectations from unbias results?

(http://www.statskingdom.com/50_ci_sample_size.html)