The minimum size of online survey. It relates how is the study population. If the study population is big and homogeneous the 100 is enough. But. When there are many variables and survey study, then the sample should minimum 5% from the population.
2. need to identity the number of Healthcare workers groups or people who have access to Internet!
3. then only you can decide the sample size using sampling method
The main types of probability sampling methods are simple random sampling, stratified sampling, cluster sampling, multistage sampling, and systematic random sampling.
when size of sample is correct then only result will come proper .
First, try to identify the objective of your survey, then for example, if it is related to prevalence rate you can use the assumption of 50% in the following formula: N= [Za2 x P x Q /(M.E.)2], with a confidence level of 95%, and an acceptable margin of 5%.
The sample size is dependent on many factors. Collecting informantion in an online survey from the right sampling element is important. For pilot studies small sample sizes , less than 30 may be acceptable. But for conclusive research a large sample size is important if N is large and it is consumer-based study.
I am shock that people are trying to answer this without more information. Sample size is not just dependent on the size of the population. What are you trying to accomplish? Are you interested in sub-populations? What is an acceptable margin of error? Can you determine how representative is your sample? Do you have information on the population so you can make adjustment to you projections? You need to answer these questions. Then you can use any of the available programs--including free online programs to make your calculations.
Determining sample size is a very important issue because samples that are too large may waste time, resources and money, while samples that are too small may lead to inaccurate results. In many cases, we can easily determine the minimum sample size needed to estimate a process parameter, such as the population mean.
If the population is known (sample size calculation with finite population) then you can use any of the following calculators to know the sample size.
Some related research paper available on researchgate:
1. Article Sample Size Determination in Health Studies: A Practical Manual.
2. Article Sample size calculation
When You have not any idea about the population ( here in your question i.e. the prevalence of any disease) so you need to use the sample size calculation with a non-finite population. (As per your nature of question).
And in this case,(sample size calculation with non-finite population) you go with the Cochran formula, for this please follow the link:
or you can visit any other link related to Cochran formula (Sorry I do not know how to type the formula here, so please go to any of the link or just search):
The following publications may further help, particularly: How large should a sample be? (see: Dillman, 2007, pp. 205-210); Sample Size (see: Lang, 2002).
Dillman, D. A. (2007) Mail and Internet Surveys : The Tailored Design Method. 2nd edn. Hoboken, New Jersey: John Wiley & Sons, Inc.
Fricker Jr., R. D. (2017) Sampling Methods for Online Surveys, in Fielding, N.G., Lee, R.M. and Blank, G. (eds.) The SAGE Handbook of Online Research Methods. 2nd ed. London: SAGE Publications Ltd, pp. 162-183.
Lang, M. (2002) The Use of Web-Based International Surveys in Information Systems Research, in Remenyi, D. (ed.) Proceedings of the European Conference on Research Methodology for Business and Management Studies (ECRM 2002, April 29-30). MCIL Reading, UK, pp. 187-196.
Prathap, D. P., Premavathi, R. and Ramasubramanian, M. (2010) The Feasibility of Conducting Online Surveys, Indian Journal of Adult Education, 71, 3, pp. 5-17.
Rahi, S. (2017) Research design and methods: A systematic review of research paradigms, sampling issues and instruments development, International Journal of Economics and Management Sciences, 6, 2, pp. 1-5.