Extremely general question.

You must specify precisely the purposes and elements of your research.

Gioacchino de Candia, Sir I hope now it is objective specific

Rekha Yadav A survey-based study in the research domain of air pollution will have a sample size that is determined by a number of criteria, including the specific research question, the population being investigated, and the desired degree of precision and power for the study.

In general, sample size calculations for survey-based research are based on the study's intended degree of accuracy and power, as well as the predicted population characteristics (e.g., mean, standard deviation) and level of confidence.

A sample size of at least 30 is generally required for a study to have appropriate power. However, depending on the exact research issue and the demographic being investigated, sample sizes bigger than 30 may be required.

Power analysis is frequently used to calculate sample size, which takes into account the required degree of precision and power, as well as the predicted population factors and the desired level of confidence.

G*Power, a sample size computation program, may also be used to calculate the suitable sample size.

The sample size for a survey-based study in the research domain of air pollution will depend on the specific research question and the population being examined. A lower sample size may be adequate, for example, if the study's goal is to estimate emissions from a given source (e.g., industrial facilities). If the study's goal is to estimate emissions from a wide range of sources across a big area, a higher sample size may be required.

Furthermore, the regional heterogeneity of air pollution must be considered. The sample size should be big enough to capture the variability in air pollution across the area of interest. However, it is worth noting that many other criteria, such as the kind of measurement, the precise sites of the measurements, and the frequency of the measurements, should be considered when planning a survey-based study in the research area of air pollution.

Finally, it is crucial to note that the number of questionnaires completed in each particular grid may not be the only metric used to calculate sample size; other parameters such as the spatial distribution of the sampling sites and the sample's representativeness should also be considered.

To ensure that the sample size is appropriate for your specific research issue and population, consult with experts in the field and analyze the existing literature.

You can find online calculators that will tell you the sample sizes needed for different levels of precision. However, note that what is important is the number of responses received, not the number invited to participate. Note also that how you draw the sample is important; a convenience sample is quite different from a random sample. I'm not clear on what you mean by mentioning individual grids. If you want to look at statistics within subsamples of the full population, then you need to think about the size of the sample within each grid, not simply overall.

Dear Rekha Yadav

I recommend online calculators in order to calculate the sample size for a descriptive aim. Here is one of the best:

https://select-statistics.co.uk/calculators/

As you would see, you have to know some information about your research, which is available in similar articles in the field. Choose the appropriate calculator, read about the fields that you have to fill in the calculator, and gather those information.

However, keep in mind that in case your aims are analytic or comparative, and you want to run tests on your data, you have to calculate another sample size which is required for achieving desirable statistical power upon running those tests. PASS software is one of the best for doing so; although I strongly recommend you to get help from a statistician if you want to use the software.

Obviously, the larger calculated sample size will be the number of participants you must seek.

Good luck