A population of different households amongst who are maize farmers. A basic formula will be of great help
Dear Langsi
Thanks for sharing your question with us. Please see the following answer, hope it would be useful. Yo can use
the following formula for the calculation of sample sizes:
n = P × (100 - P) × z2/d2
where P is the anticipated prevalence d is the desired precision z is the appropriate value from the normal distribution for the desired confidence
level of confidence 90, 95 and 99 percent are as z = 1.645, z = 1.960, z = 2.576 , respectively.
For more information you can visit the following website:
https://www.slideshare.net/zubis/sample-size-13281869
With best regards
Behzad Sadeghzadeh
U can randomly sample a percent of the popn over the period of you sampling. But it has to be practical.
Dear Langsi
Thanks for sharing your question with us. Please see the following answer, hope it would be useful. Yo can use
the following formula for the calculation of sample sizes:
n = P × (100 - P) × z2/d2
where P is the anticipated prevalence d is the desired precision z is the appropriate value from the normal distribution for the desired confidence
level of confidence 90, 95 and 99 percent are as z = 1.645, z = 1.960, z = 2.576 , respectively.
For more information you can visit the following website:
https://www.slideshare.net/zubis/sample-size-13281869
With best regards
Behzad Sadeghzadeh
Langsi -
With a large population, you are likely to do much better with stratified random sampling than simple random sampling.
Estimation of population, or strata standard deviations is important, and a pilot study may be useful for this.
Here are a couple of good textbook references:
Cochran, W.G(1977), Sampling Techniques, 3rd ed., John Wiley & Sons.
Thompson, S.K.(2012), Sampling, 3rd ed, John Wiley & Sons.
Cheers - Jim
PS - Be careful of online sample size calculators and formulas you may often be given, as they are often only good for yes/no questions (sometimes for the worst case situation), and only simple random sampling, and with no finite population correction (fpc) factor, though you likely need no fpc here.
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