In experiments that depends on a group of people, animals, living organisms, and contains questionnaire and statistical analysis, it is important to have as much large as possible population size to get accurate results and percentages. What should be the minimum size population involved to obtain a high accuracy and precision?
Dear Fatemah,
You can calculate your needed sample size. Free sample size calculators are on the net.
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Dear Fatemah,
You can calculate your needed sample size. Free sample size calculators are on the net.
Article Power and sample size determination for the group comparison...
Article Estimating the sample size for a pilot randomised trial to m...
Article Sample Size Calculations for Clustered and Longitudinal Outc...
I believe that you mean "sample" and not "population". A sample is a subset of the population that is used for study. Populations are never studied in their entirety. See the link below for a primer on sample size calculations.
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2876926/
Fatemah
Gordon is correct and Beatrice correctly inferred - it is sample size you want which is determined from knowledge of the population.
A simple calculator for this (with some basic explanations) can be found here:
http://www.surveysystem.com/sscalc.htm
Yes, you are correct, it is a sample, as it is a specific statistical term that may confuse a biologist. Thanks a lot all for your valuable answers.
"Among the questions that a health worker should ask when planning a survey or study is "How large a sample do I need?" The answer will depend on the aims, nature and scope of the study and the expected results, all of which should be carefully considered at the planning stage."
Hope the attached file be helpful for you.
Thanks Dr. Mahdi for your answer. By the way, there is a missing part in the file attached concerning the tables of minimum sample size.
Fatemah -
I have an answer to the question at the following URL that may be of interest to you:
https://www.researchgate.net/post/Are_there_any_methods_or_criteria_for_calculating_the_Sample_Size_Calculation_for_Research
It all depends upon your application.
Cheers - Jim
Dear Fatemah
You can use the following formula to estimate the sample size according to your information about the population which the sample will be taken from it :
Sample size from finite population can be estimate by :
n= N / ( 1+ N * e^2 )
and from infinite population by :
n= ( Z^2 * S^2) / E^2
where : Z ( 1.96 for 0.05 and 2.58 for 0.01 )
S = standard deviation from previous studies or pilot study
E = significant level
Also, you can use software to calculate sample size ( SPSS , Minitab , Gpower )
For more information you can read the attached files:
322830.pdf
How to Calculate Sample Size for Di...dy Designs in Medical Research_.pdf
KrejcieandMorgan_article.pdf
Thanks a lot Dr. Kalid Hassan for your answer. Excuse me I can not reach the attachments.
Dear Fatemah
I am sorry for incomplete link in previous answer ,you can use the following attachments .
Good Luck
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