Sample size table - sample sizes for Estimation Test Plan

Use the sample size table to choose the sample size necessary to estimate a percentile or reliability with the specified amount of precision.

If you provided a right-censoring time in the Right Cens subdialog box, Minitab displays this value as the censoring time.

The precision is the distance between your percentile or reliability estimate and the upper (or lower) bound of the 1-sided confidence interval for that estimate. If you provide multiple values for the precision, Minitab displays them in separate rows of this table.

The sample size is the number of units you must test to obtain that level of precision. Because the sample size must be rounded to the nearest integer value, you cannot exactly achieve your target confidence level. Minitab displays the actual confidence level for that sample size, which is slightly higher than the target confidence level.

Example output

Test Plans

Censoring Time	Precision	Sample Size	Actual Confidence Level
1000	100	354	95.0011
1000	200	61	95.0892
1000	300	15	95.1695

Interpretation

For the insulation data, with a censoring time of 1000 hours and a target confidence level of 95% for a 1-sided confidence interval, you must test the following:

354 units to estimate a lower bound for the 10th percentile within 100 hours with 95.0011% confidence
61 units to estimate a lower bound for the 10th percentile within 200 hours with 95.0892% confidence
15 units to estimate a lower bound for the 10th percentile within 300 hours with 95.1695% confidence