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of the Commonwealth of Pennsylvania

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    Flowchart for Calculating Rates and Confidence Intervals

     

    Process for Calculating Measures and Their Reliability

    1. Are there 20 or more events?
    2. Can you group the data with a wider range of years or neighboring geographic areas?
      • No: Go to step 3.
      • Yes: Go to step 1.
    3. Are there between 10 and 19 events?
      • No: Population-level statistics will be unreliable.  Consider case reviews for analysis.
      • Yes: Use either the crude rate or the standardized ratio, with the relevant confidence interval.

    Crude Rate

    "Crude rate" is another term for an unadjusted rate.  The denominator is usually a population withan an area, but could be a specific subgroup. The choice of denominator depends on the what the rate should show. For example, general fertility is the rate of births among females of childbearing age.

    See Definitions of Rates Used in Public Health Assessment (PDF) to calculate a crude rate.

    See Confidence Intervals for a Crude Rate (PDF) to calculate a 95% confidence interval.

    Adjusted Rate

    See Age-Adjusted Rates to calculcate an adjusted rate.

    See Confidence Intervals for an Age-adjusted Rate (PDF) to calculate a 95% confidence interval.

    Standardized Ratio

    See Standardized Mortality Ratio to calculate a standardized ratio.

    See Confidence Intervals and Significance Testing for a Standardized Ratio (PDF) to calculate a 95% confidence interval.