Sample Size Calculator

N is the number of people in the population.  

z = z-score, i.e., desired confidence level

e = margin of error (% in decimal form)

The number of standard deviations a proportion is distant from the mean is represented by the z-score. Refer to the chart below to determine which z-score to use: 

Example: If you want to use a 95 percent confidence level, standard deviation of 0.5, and confidence interval (margin of error) of 5%, you can simply change the values in the formula:

e = ((1.96)2 x .5(.5)) / (.05)2 

e = (3.8416 x .25) / .0025 

e = .9604 / .0025 

e = 384.16 

Your sample size should be 385. 

You can leverage a sample size calculator to evaluate the efficacy of your survey sample. The calculator can help you mitigate human error and calculate the size faster. 

Before you start calculating the right size of respondents, you should learn more about certain nuances. 

1. Margin of Error or Confidence Interval
2. Confidence Level
3. Population Size
4. Standard Deviation

Let’s discuss these three factors in brief. 

1. Margin of Error or Confidence interval: 

Margin of error indicates how certain you may be that the findings of a study match what you would expect to discover if the whole population being investigated could be surveyed. 

Usually, the confidence interval is expressed as a plus or minus number. 

If your confidence interval is 7 and 70% of your sample chooses a response, you can be certain that if you surveyed the entire population, 63 percent (70-7) and 77 percent (70+7) would choose that response. 

2. Confidence level: 

The percentage will tell you how confident you can be that the real population taking your survey will choose an answer from the available options. 

It’s expressed as a percentage and indicates how often the percentage of people who would choose a particular response falls inside the confidence interval. 

For example, a 99 percent confidence level suggests that if you repeat a poll repeatedly, your results will match those of a population 99 percent of the time. 

3. Population Size:

Population size is the total number of audience you want to gather data on, the total no. of people you want to survey. 

For example, if you want to gather data from Japanese residing in Australia, your population size would be approx. 93.5 thousand (as of October 2021). 

4. Standard deviation: 

The standard deviation, which gauges a data set’s distribution from its mean, is another essential factor to consider when calculating sample size. 

The standard deviation can be used to estimate how much the replies you receive will differ from each other and the mean when determining the sample size. We can use a sample’s standard deviation to approximate a population’s standard deviation.

Learning about these factors that affect the statistical significance is better, especially when using a sample size calculator. This will help you uncover where the problem lies and allow you to fix it faster.