To calculate a test and confidence interval for the difference in Poisson rates
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1    Choose Stat > Basic Statistics > 2-Sample Poisson Rate

2    Do one of the following:

·    If data from both samples are stacked in a single column:

1    Choose Both samples are in one column.

2    In Samples, enter the columns containing the samples' data.

3    In Sample IDs, enter the column containing the subscripts identifying from which sample each item originates.

4    If your column of stacked data contains only unique values, enter a separate column of their corresponding frequencies in Frequency column.

·    If data from both samples exist in separate columns (unstacked form):

1    Choose Each sample is in its own column.

2    In Sample 1, enter the column containing the first sample.

3    In Sample 2, enter the column containing the second sample.

4    If, for each sample, you have a column of unique values and a separate column of corresponding frequencies, enter the columns of frequencies in Frequency columns.

·    If you have summarized data:

1    Choose Summarized data.

2    In Sample 1, enter values for Sample size and Total occurrences for the first sample.

3    In Sample 2, enter values for Sample size and Total occurrences for the second sample.

3    If you like, use any dialog box options, and click OK.