Testing

Statistical power

Statistical power is the probability of getting meaningful results from a test.

Usually, you need a statistical power of at least 0.8 or 80% to consider your results statistically significant.

Statistically significant

If a test is statistically significant, it means the results of the test are real and not an error caused by random chance.

Hypothesis testing

Hypothesis testing is a way to see if a survey or experiment has meaningful results.

Confidence level

The confidence level is the probability that your sample accurately reflects the greater population.

Having a 99 percent confidence level is ideal. But most industries hope for at least a 90 or 95 percent confidence level.

Sample size calculator

To calculate the sample size, we need, population size, confidence level, margin of error.

There are some terms you will come across when using a sample size calculator:

• Confidence level: The probability that your sample size accurately reflects the greater population.

• Margin of error: The maximum amount that the sample results are expected to differ from those of the actual population.

• Population: This is the total number you hope to pull your sample from.

• Sample: A part of a population that is representative of the population.

• Estimated response rate: If you are running a survey of individuals, this is the percentage of people you expect will complete your survey out of those who received the survey.

Margin of error

The maximum amount that the sample results are expected to differ from those of the actual population. More technically, the margin of error defines a range of values below and above the average result for the sample.

The closer to zero the margin of error, the closer your results from your sample would match results from the overall population.

So to calculate margin of error, you need three things:

• population size
• sample size
• confidence level.