This is a blur area in the bibliography I study, and the numbers used are mostly rounded up (N=500, N=1000 etc) without any other explanation. What would you suggest?
You can find the basic formula and assistance in computing sample sizes with an internet search for "sample size calculator."
There are several methods that you can use to calculate the sample size needed for your research. Some common methods include:
It's important to note that the sample size needed for a study is not always fixed and may need to be adjusted based on the results of the study. It's also important to carefully consider the potential biases and limitations of your sample when interpreting the results of your research
David L Morgan thank you very much for your answer! I wonder if there is a connection to the number of the hypotheses that I am checking or the number of questions in the questionnaire I am using. Any advice would be helpful! Thank you in advance, MG.
Sushil Humane thank you for your answer! I tried the calculator you suggest and I have a result. From your experience,do you know if this calculator is credible enough to mention it in the manuscript or do you suggest another more popular one? Thank you in advance, MG.
Jamal Tikouk thank you very much for your detailed and helpful answer! I already tried the way of the calculation formula and I downloaded the G Power software to try the power analysis that you proposed. However, the number that the formula suggests is way bigger than the one of the power analysis. How can I figure out which one is correct answer? Thank you in advance, MG.
To determine which sample size is the most appropriate for your study, it may be helpful to consider the resources and constraints of your research project. If the sample size recommended by the power analysis is not feasible given your resources or the constraints of your study, you may need to consider adjusting your research design or your assumptions about the desired level of power or the expected effect size. Alternatively, you may need to reconsider the importance of the research question and whether it is worth pursuing given the limitations of your resources
If your main goal is to estimate values in the larger population, then the formula using the estimated variance makes the most sense. Alternatively, if your goal is to test specific hypotheses, then G*Power might be better suited to your objective.s
Jamal Tikouk thank you very much for your helpful advice! I will see what I can do!
David L Morgan thank you very much for your advice and your quick reply! This makes sense to me, too. I will reconsider the direction towards where I am heading and choose the most appropriate method. I think I have a justified answer for the size of my sample now, and not just rounded up numbers. You have been very helpful! If you think of any other tips, feel free to share!
Formula to calculate the sample size:
n = (z2*p*q)/d2
Here,
n = Desired sample size
z = Standard normal deviate; z value is 1.96 for 95% confidence interval (CI).
P = population proportion from previously published similar kind of study.
q = (1 – p)
d = Degree of accuracy desire, usually set at 0.05
Non response 10% will be added.
Marilena Gialama The sample size required for a research study is determined by several criteria, including the population size, the desired level of precision, and the level of confidence in the results. There are various ways for computing sample size, including power estimates that take effect size, alpha, and power levels into consideration.
Power calculations are a typical way for estimating sample size. The minimal number of participants required to detect a statistically significant difference between groups or to detect a specific effect size is determined using this approach. The sample size calculation considers the intended level of power (often 80% or 90%), the level of significance (typically 0.05), and the estimated impact.
The use of sample size calculators, which are accessible online and may help you predict the number of participants needed for a research depending on the criteria you enter, is another approach of establishing sample size.
It is also critical to assess the possibility of attracting and keeping the necessary number of participants. If a bigger sample cannot be recruited, a smaller sample size may be appropriate.
In conclusion, establishing sample size is a crucial phase in the research process and should be based on the research topic, population size, desired level of precision, and intended level of confidence in the results. It is suggested that sample size calculation tools or power analysis be used to determine the appropriate sample size.
It depends on the type of sampling method you are using pending the nature of your study. For example, Random sampling can utilise the common random sampling formula, (see https://www.surveysystem.com/sscalc.htm).
However, if you are using purposeful sampling, then you just need to justify why you require a specific sample size and the type of respondents thereof.
You may also try a census approach whereby you can target an entire 'population' within a given space/time (This is usually used when the population size is relatively limited). Goodluck
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