This procedure can calculate power, sample size and minimum difference for the 1-Sample Z test.
1. Choose ProcessMA > Statistics > Power and Sample Size > 1-Sample Z.
2. In Objective, choose what you want to calculate.
· If you want to find sample size(s):
- In Difference(s), enter one or more differences, separated by commas(,).
- In Power value(s), enter one or more power values, separated by commas(,).
· If you want to find difference(s):
- In Sample size(s), enter one or more sample sizes, separated by commas(,).
- In Power value(s), enter one or more power values, separated by commas(,).
· If you want to find power value(s):
- In Sample size(s), enter one or more sample sizes, separated by commas(,).
- In Difference (s), enter one or more differences, separated by commas(,).
3. In Standard deviation, enter the population standard deviation.
4. In Alternate, select the type of test.
5. In Significance level, enter the desired significance level.
6. Click OK.
Sample size(s): Integer.
Difference(s): Numeric.
Power value(s): Numeric; Between 0 to 1; Must be greater than the significance level.
Standard deviation: Numeric.
You are the quality assurance manager for a printer cartridge plant. You need to ensure that printer cartridges are filled with a 60ml of ink and cannot vary more than ±2ml. You know from past records that the standard deviation is 3ml. Determine how many samples you need to take at a confidence level of 99% (a = 0.01) and power values of 0.8 and 0.9?
1. Choose ProcessMA > Statistics > Power and Sample Size > 1-Sample Z.
2. In Objective, select Find sample size(s).
3. In Differences(s), enter 2.
4. In Power value(s), enter 0.8, 0.9.
5. In Standard deviation, enter 3.
6. In Alternate, select Not equals.
7. In Significance level, enter 0.01.
8. Click OK.
Interpretation
You need to take 27 and 34 samples, and the power for your test is 0.8128 and 0.9052 respectively to achieve a 99% level of confidence.