Power and Sample Size

Overview | How to | Example

 

 

Overview

This procedure can calculate power, sample size and minimum difference for the 1-Sample Z test, 1-Sample t, 2-Sample t, 1 Proportion, 2 Proportions, One-Way ANOVA. It also includes a simple sample size calculator for both continuous and discrete data.

 

 

How to

At the Excel Menu (For Excel 2007, go to Add-ins first)

  1. Choose ProcessMA > Statistics > Power and Sample Size

  2. For 1-Sample Z:
    1. Enter data in Cells D6:D11
    2. For sample size, difference and power value, provide values in any 2 to calculate the other
    3. Results will be displayed in Cell D13
  3. For 1-Sample t:
    1. Enter data in Cells D16:D21
    2. For sample size, difference and power value, provide values in any 2 to calculate the other
    3. Results will be displayed in Cell D23
  4. For 2-Sample t:
    1. Enter data in Cells D26:D31
    2. For sample size, difference and power value, provide values in any 2 to calculate the other
    3. Results will be displayed in Cell D33
  5. For 1 Proportion:
    1. Enter data in Cells G6:G11
    2. For sample size, difference and power value, provide values in any 2 to calculate the other
    3. Results will be displayed in Cell G13
  6. For 2 Proportions:
    1. Enter data in Cells G16:G21
    2. For sample size, difference and power value, provide values in any 2 to calculate the other
    3. Results will be displayed in Cell G23
  7. For One-Way ANOVA:
    1. Enter data in Cells G26:G31
    2. For sample size, max difference and power value, provide values in any 2 to calculate the other
    3. Results will be displayed in Cell G33
  8. For Continuous data (Simple sample size calculator):
    1. Enter data in Cells D36:D38
    2. Results will be displayed in Cell D40
  9. For Discrete data (Simple sample size calculator):
    1. Enter data in Cells G36:G38
    2. Results will be displayed in Cell G40
 

 

Example

For 1-Sample Z, 1-Sample t, 2-Sample t, One-Way ANOVA and Simple Sample Size Calculator for continuous data:
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?

For 1 Proportion, 2 Proportions and Simple Sample Size Calculator for discrete data:
You are the logistic manager and you need to find out if the proportion of products damaged during transport changed after using a new packaging. Historically the proportion of goods damaged during transport is 0.1. Determine the number of samples you need to detect a difference of 0.05 at a confidence level of 95% (a = 0.05) for a power of 0.9?

  1. Choose ProcessMA > Tools > Load Examples

  2. In Category, select Statistics

  3. In Tool, select Power and Sample Size

 

Results & Interpretation

Sample sizes for the various tests are calculated.

 

 

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