This calculator calculates the confidence level, number of samples, or number rejects allowed to satisfy a set of given conditions for a one shot device. The calculations are based on the Binomial Distribution and the following formula:
 |
| |
Confidence Level (CL) = |
 |
|
|
| where: |
| n | = | sample size |
| p | = | proportion defective |
| r | = | number defective |
 | = | probability of k or fewer failures occurring in a test of n units |
|
| Example use of the Calculator: |
| Assume that you need to be 95% confident that your product is no more than 10% defective. You tested 60 samples and 3 were found to be defective. Did you meet the goal of 95% confidence? Using the calculator, input p = .1, n = 60, r = 3, and calculate for CL. You would only be 86.26% confident that your product is no more than 10% defective. |
| Enter: | p | = | 0.10 |
| | n | = | 60 |
| | r | = | 3 |
| Press Calculate |
| Solves for: | CL | = | 86.26% |
|
| What is the maximum number of defects in a sample size of 60 that would yield a 95% confidence level that the product was no more than 10% defective? Using the calculator, input p = .1, n = 60, CL = 95, and calculate for r. The number of defectives allowed would have been 1. |
| Enter: | p | = | 0.10 |
| | n | = | 60 |
| | CL | = | 95 |
| Press Calculate |
| Solves for: | r | = | 1 |
|
| Knowing that you had 3 defects, what minimum sample size is needed to be 95% confident that the product is no more than 10% defective? Calculator inputs are p =.1, r = 3, CL = 95, and calculate n. The minimum sample size will be 76. |
| Enter: | p | = | 0.10 |
| | r | = | 3 |
| | CL | = | 95 |
| Press Calculate |
| Solves for: | n | = | 76 |
|
CAUTION:
The calculator is capable of handling large sample sizes (n) and number defective (r) values. If n is greater than (>) 1,500 and r is greater than (>) 100, the calculation may take an excessive amount of time. |
|
