My PhD research proposal is to determine the impact of climate change on farmers in the different agro-climatic zone of West-Bengal. I am quite confused to frame the sample size as I am not getting the proper theory to fit against the farming population of Bengal.
Use at least n = 30 to fulfil the central limit theorem :)
n = z² x p ( 1 – p ) / m²
n = sample size
z = level of confidence according to the reduced centred normal distribution (for a level of confidence of 95%, z = 1.96, for a level of confidence of 99%, z = 2.575)
p = estimated proportion of the population that presents the characteristic (when unknown, use p = 0.5 which corresponds to the most unfavourable case, i.e. the greatest dispersion)
m = tolerated margin of error (for example we want to know the real proportion to within 5%)
This formula determines the number of people n to be interviewed according to the margin of error m that can be tolerated on a proportion of answers p.
Examples:
1. To calculate a proportion with a 99% confidence level and a 2% margin of error:
n = (2.575)² x (0.5)(1- 0.5) / (0.02)² = 4144.14
2. To calculate a proportion with a 95% confidence level and a 5% margin of error:
n = (1.96)² x (0.5)(1- 0.5) / (0.05)² = 384.16
3. To calculate a proportion with a 95% confidence level and a 7% margin of error:
n = (1.96)² x (0.5)(1- 0.5) / (0.07)² = 196
Regards
Hello Sourakanti; Here is a reference that might help.
Ruxton, GD and N Colegrave, 2003.
Experimental design for the life Sciences. Oxford Univ Pr. 162 p.
Best regards; Jim Des Lauriers
Dear Sourakanti Sarkar . See the following useful link: Article Sample size calculation
Kindly see also the following useful RG link: Article A Step-by-Step Process on Sample Size Determination for Medi...
Also check please the following useful links: https://www.bebr.ufl.edu/sites/default/files/Sampling%20and%20Estimation%20in%20Hidden%20Populations.pdf
https://www.statisticshowto.com/probability-and-statistics/find-sample-size/
The following links are also very useful: https://stateoftalent.org/topic/fa7413-how-to-determine-sample-size-for-unknown-population
https://m.youtube.com/watch?v=m8w12OF2xnw
These links maybe useful
MLPowSim | Centre for Multilevel Modelling | University of Bristol
http://www.bristol.ac.uk/cmm/software/mlpowsim/
Sample Size Calculator
https://www.calculator.net/sample-size-calculator.html
First you need to know what you are doing and what your choices are..So get a good research question and then your design. For the sampling plan see Schaefer et al Elementary Survey Sampling from the z-library and read it carefully. At this point you will be ready to compute your needed sample size and how it will be allocated.amomg.the population. Get a resesrch design.book, I recomend the one by Lawson in the attachment, download it from the z-library. Put this all.together and you should have a great research design
Best wishes David Bootj
PS be sure what you wish to understand from this research is clear in your mind.
In addition let me say that the research goal expressed is way to general.. pick a type of farming and look at the effect of rainfall.change on the crop yields. A classic paper by R A FISHER is attached and should be helpful with your design. Please ask questions if you have them best wishes David Booth
Use Cochran or Solvins formula for sample size of known as well as unknown population.
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