Dear Hailemichael Kindie

without knowing your intended calculations, this is impossible to determine. I would refrain from using often unattainable "rules of thumb" like x participants per variable. You will not only find a number of threads on RG that have dealt with this question, but a mountain of literature on the topic of statistical power. One of the most precise, yet difficult procedures would be a Monte Carlo simulation - I am struggling with those myself at the moment.

Good luck!

Marcel

I would highly agree with Marcel Grieger .

You would not want to base your study on assumptions.

I think you need to calculate the power of analysis (beta risk) with known characteristics of the population.

To calculate a sample size, you need to have information on study design, population size, significance level, power level, effect size, margin of error, and standard deviation. The review article by Sharma et al. (2019), attached and referenced below, could provide in-depth insights.

Sharma, S., Mudgal, S., Thakur, K., & Gaur, R. (2019). How to calculate sample size for observational and experiential nursing research studies? National Journal of Physiology, Pharmacy and Pharmacology, 0, 1. https://doi.org/10.5455/njppp.2020.10.0930717102019

Good luck,

Hailemichael Kindie

The standard error is inversely proportional to the variance (s.d.2) of the number of participants/observations etc. The answer above by Mohialdeen Alotumi is correct. What acceptable margin of error do you require in your analysis?

Hi..at the 1st place the observation is one of the data collection method in QUALITATIVE data NOT QUANTITATIVE.

Here I share with you my writing of justification in determine the no of samples for key-informants. Sorry because I don't have the right answer for your question. Maybe this sharing can helps you. Tq.

Key informant interviews for qualitative data.

There are many types of qualitative methods. For example, (Creswell (1994) identified five qualitative research paradigms which are biography, phenomenology, grounded theory, case study and ethnography study. Most importantly, the qualitative methods can answer the research questions and illuminates issues that cannot be addressed by quantitative methods (Singh et al., 2006). There are a few interview techniques in conducting qualitative field research, namely qualitative interview, focus group, recording observations, qualitative documents and qualitative audio and visual materials (Babbie, 2010; Creswell, 2009).

This study employed a qualitative research design by conducting interview with the key informants. Key informants are people who know about the topic being studied (Heinen, 2010; Singh et al., 2006; Walter, 2010). The interview employed in this study is different with survey method because it is based on a set of topics that need to be discussed in-depth rather than based on the use of standardised questions. The key informant interviews involved interviews with a selected group of individuals who can probably provide the needed information, ideas and opinion on a particular subject.

As a rule of thumb, the number of key informants that usually ranges from 15 to 35 is sufficient for most social studies (K. Kumar, 1989). If the research combines different types of data collection methods, such as surveys, document content analysis and key informant interviews, fewer key informants may be sufficient (K. Kumar, 1989). For example, Wilson and Wiber (2009)employed a snowball sampling technique to identify 14 key informant interviews who were drawn from nine organisations in relation to community involvement in community based integrated coastal management at Annapolis Basin, Canada.

Aheto et al. (2016) interviewed 25 members of the mangrove planters association to assess the success of community-based approaches in coastal resource management along the Volta estuary of Ghana. Generally, the decision on the number of key informants to interview are based on the availability of time and resources, complexity of the issues involved and the information available from other sources.