Sample Size Power Calculation


Power analysis is crucial in experimental design, helping researchers determine the minimum sample size required to detect a significant effect. Our Sample Size Power Calculation tool simplifies this process, considering factors such as effect size, significance level (α), and desired power.


The formula for calculating the sample size in a power analysis involves the effect size, significance level, and desired power. It utilizes the Z-scores corresponding to the significance level (α) and power to determine the required sample size.

How to Use

  1. Enter the effect size, representing the magnitude of the difference or effect you expect to detect.
  2. Input the significance level (α), typically set at 0.05 for a 95% confidence level.
  3. Specify the desired power, representing the probability of detecting a true effect if it exists.
  4. Click the “Calculate” button to obtain the recommended sample size.


Suppose you are designing a study to investigate the impact of a new treatment with an expected effect size of 0.5, a significance level of 0.05, and a desired power of 0.8. Input these values to determine the sample size needed for a robust analysis.


  1. Q: Why is power analysis important in research studies?
    • A: Power analysis ensures that a study has a sufficient sample size to detect a significant effect if it exists.
  2. Q: Can I use this calculator for different significance levels?
    • A: Yes, you can input any significance level within the valid range to customize your calculation.
  3. Q: How does the effect size impact the sample size in power analysis?
    • A: A larger effect size typically requires a smaller sample size for detection.
  4. Q: Is a higher power always preferable in a study?
    • A: Higher power increases the likelihood of detecting a true effect but may require a larger sample size.
  5. Q: What is the default Z-score used in the calculation?
    • A: The calculator uses a Z-score of 1.96 for a two-tailed test with a 95% confidence level. You can adjust this value if needed.


Our Sample Size Power Calculation tool empowers researchers to optimize their study design by determining the sample size needed for a robust analysis. Use this calculator to enhance the reliability and validity of your research findings, ensuring meaningful and impactful results.

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