Sample size calculator
Plan estimation precision with explicit population and confidence inputs.
روش استفاده Sample size calculator
The Sample size calculator returns the number of responses needed to estimate a single proportion with a chosen confidence level, margin of error and expected proportion. It uses n = z² × p(1 − p) / e² and applies a finite population correction when you enter a population size. The result is rounded up to a whole respondent and assumes random sampling.
- Enter the requested values in the settings panel.
- Adjust the basic settings, then open Advanced mode for export and fine-tuning options. Custom settings stay active when the panel is closed.
- Run sample size calculator, review the output, then use the available copy or download controls.
قابلیتهای این ابزار
Plan estimation precision with explicit population and confidence inputs.
- Confidence (%)
- Range: 50 to 99.99
- Absolute proportion margin (%)
- Range: 0.01 to 49
- Expected proportion (%)
- Range: 0.01 to 99.99
- Population (0 = unbounded)
- Range: 0 to 1000000000000
محدودیتها و پردازش
Local bounded calculations. Numeric inputs must be finite and within the visible ranges. Lists and tables have operation-specific limits. Models, estimates and supplied rates must be checked against your intended use.
پرسشهای متداول
How is sample size calculated for a survey?
The base size is n0 = z² × p × (1 − p) / e², where z comes from the confidence level, p is the expected proportion and e is the margin. At 95% confidence, a 5% margin and p = 50%, n0 is about 384.1, which rounds up to 385.
How does population size affect the required sample?
With Population set to 0, the population is treated as unbounded. Entering a population size N applies the correction n0 / (1 + (n0 − 1) / N), which lowers the required sample for small populations. A population of 1 is rejected.
Why use 50% as the expected proportion?
p × (1 − p) is largest at 50%, so it gives the most conservative, largest sample size when you do not know the likely result. If earlier data suggests a proportion such as 10%, entering it produces a smaller required sample.
Where is my input processed?
This operation processes its source in your browser. Copy and download are explicit actions; source input is not saved in an account or history.
What are the input limits?
Local bounded calculations. Numeric inputs must be finite and within the visible ranges. Lists and tables have operation-specific limits. Models, estimates and supplied rates must be checked against your intended use.