Sample Size Calculator | Industrial Engineering Calculators

Sample Size Determination

Sample size calculation is essential for designing effective quality control procedures, surveys, and experiments. The appropriate sample size depends on your specific objectives and the characteristics of your population.

Sample size formulas vary based on the calculation scenario

Select the appropriate scenario below based on your needs:

Calculation Scenario

Choose what you want to calculate:

Proportion (Defect Rate)

Mean (Average)

Finite Population

Sample Size for Proportion (Defect Rate)

Calculate sample size needed to estimate a proportion (like defect rate) with specified confidence and precision.

Population Size (leave blank if unknown):

Estimated Proportion (0-1, e.g., 0.05 for 5%):

Confidence Level:

Margin of Error (e.g., 0.05 for ±5%):

Result

Required Sample Size:

Interpretation

To estimate the defect rate within ± with % confidence, you need a sample size of .

Sample Size for Mean (Average)

Calculate sample size needed to estimate an average value with specified confidence and precision.

Population Size (leave blank if unknown):

Estimated Standard Deviation:

Confidence Level:

Margin of Error (units of measure):

Result

Required Sample Size:

Interpretation

To estimate the average within ± with % confidence, you need a sample size of .

Sample Size for Finite Population

Calculate sample size needed when sampling from a small, known population.

Population Size:

Confidence Level:

Margin of Error (0-1, e.g., 0.05 for ±5%):

Estimated Proportion (0-1, default 0.5 for max variability):

Result

Required Sample Size:

Interpretation

For a population of , to estimate with ± margin of error at % confidence, you need a sample size of .

Practical Examples

Quality Control Example

Estimating defect rate in a production batch:

Population: 10,000 | Estimated Defect Rate: 2% | Confidence: 95% | Margin: ±1%

Sample Size Needed: 753 (without FPC) or 690 (with FPC)

Process Improvement Example

Measuring average processing time:

Std Dev: 2.5 minutes | Confidence: 95% | Margin: ±0.5 minutes

Sample Size Needed: 96 observations

Employee Survey Example

Surveying satisfaction in a small company:

Population: 150 employees | Confidence: 95% | Margin: ±5%

Sample Size Needed: 108 employees

Sample Size Guidelines

Population Size	Recommended Sample Size
100	80
1,000	278
10,000	370
100,000	383
1,000,000+	384

Note: Based on 95% confidence level and ±5% margin of error for proportions