How do you select the best sample size for your community needs assessment?

1 Define your population

Before you can calculate your sample size, you need to define your population of interest. This is the group of people or units that you want to generalize your findings to. For example, if you are assessing the needs of low-income families in a certain city, your population would be all the low-income families living in that city. You need to have a clear idea of who belongs to your population and how many of them there are. This will help you avoid sampling errors and biases.

2 Choose your sampling method

Next, you need to choose your sampling method. This is the way you select a subset of your population to participate in your data collection. There are different types of sampling methods, such as random, stratified, cluster, convenience, or snowball. Each method has its own advantages and disadvantages, depending on your research question, design, and resources. You should choose a sampling method that fits your purpose, budget, and timeline, and that ensures the representativeness and diversity of your sample.

3 Determine your margin of error and confidence level

Another factor to consider is your margin of error and confidence level. These are statistical terms that indicate how much uncertainty there is in your sample results and how confident you are that they reflect the true situation of your population. The margin of error is the maximum difference between your sample results and the population results, expressed as a percentage. The confidence level is the probability that your sample results are within the margin of error of the population results, expressed as a percentage. For example, if you have a margin of error of 5% and a confidence level of 95%, it means that you are 95% sure that your sample results are within 5% of the population results. The smaller the margin of error and the higher the confidence level, the more accurate and reliable your sample results are. However, this also means that you need a larger sample size to achieve them.

4 Use a sample size calculator

Finally, you can use a sample size calculator to estimate how many people or units you need to include in your data collection. A sample size calculator is a tool that uses a formula to calculate the sample size based on your population size, sampling method, margin of error, and confidence level. You can find various online sample size calculators that are easy to use and free of charge. However, you should also be aware of the limitations and assumptions of these calculators, and consult with a statistician or an expert if you have any doubts or questions.

5 Here’s what else to consider

This is a space to share examples, stories, or insights that don’t fit into any of the previous sections. What else would you like to add?