Enter your data for Power and Sample Size for 2-Sample Poisson Rate

Stat > Power and Sample Size > 2-Sample Poisson Rate

Complete the following steps to specify the data for the power and sample size calculation.

  1. Specify values for two of the following power function variables. Leave the variable that you want to calculate blank.
    • Sample sizes: Enter the number of observations for each group. For example, enter 50 to indicate that you will collect 50 observations for each of the two groups. To assess the effect of different sample sizes, enter multiple values. Larger sample sizes give the test more power to detect a difference.

      If you enter multiple values into a field, separate the values with a space. You can also use shorthand notation to indicate multiple values. For example, you can enter 10:40/5 to indicate sample sizes from 10 to 40 in increments of 5.

    • Comparison rates (R1): Enter one or more rates that are meaningfully different from the Baseline rate (R2). If you conduct a before/after analysis, enter the after rate here. Usually, the difference between the comparison rate and baseline rate is the smallest difference that has practical consequences for your application.

    • Power values: Enter one or more values to specify the probability that the test detects a difference between the rates when a difference actually exists. Common values are 0.8 and 0.9. For example, a shoe manufacturer enters 0.9 to have a 90% chance that the test will detect an important difference between the rate of defects of two factories when a difference actually exists.
  2. In Baseline rate (R2), enter the rate to which you want to compare the Comparison rates (R1). If you conduct a before/after analysis, enter the before rate here.