Include Rate Ratios on Last Row Variable Groupings

If you are calculating crude or age-adjusted rates, you can select this option on the Statistic tab in a Rate session to calculate ratios comparing rates. The first grouping of the last row variable in the analysis is used as the reference grouping (the denominator of the ratio), and the rate for each subsequent grouping is compared (the numerator of the ratio) to the reference grouping's rate. Four additional columns, containing the rate ratio and related statistics, will be displayed in your Rate results matrix.

Unless the grouping you want to compare is already the first grouping of its standard variable, you must create a user-defined variable with groupings reordered appropriately. On the Table tab, make this user-defined variable the last (bottom-most) row variable.

When this option is selected, the option to Show Standard Errors and Confidence Intervals will be automatically selected as well, and cannot be changed. Confidence intervals for the rate ratios are among the additional statistics displayed in the results matrix.

When you execute the session, if this option is marked, but no row variable has been specified on the Table tab, SEER*Stat will warn you of this fact and give you the option to execute the session anyway, omitting the rate ratios.

If the reference grouping overlaps with any of the variable's other groupings, SEER*Stat will warn you of this fact as well. If the variable is a merged variable, you will always get this warning, since SEER*Stat cannot determine whether merged variable groupings contain overlapping values. The algorithms for the standard errors and confidence intervals assume that there is no overlap; however, if the overlap is minor, the imprecision may not seriously bias the results. You must use your own judgment in deciding whether to ignore this warning. If you do proceed despite this warning, the matrix footnotes will contain a note about the overlap.

Example

Suppose you want to compare the rate of breast cancer incidence among white females to the rates among black females and females of other races during the years from 1997 to 2001.

  1. On the Data tab, select an Incidence database that includes the years 1997-2001.

  2. On the Statistic tab, choose Rates (Age-Adjusted), and mark the Include Rate Ratios on Last Row Variable Groupings checkbox.

  3. On the Selection tab, edit the "Race, Sex, Year Dx, Registry, County (Pop, Case Files)" selection statement to read:

    {Race, Sex, Year Dx, Registry, County.Sex} = 'Female'
    AND {Race, Sex, Year Dx, Registry, County.Race recode A} = 'White','Black','Other'
    AND {Race, Sex, Year Dx, Registry, County.Year of diagnosis} = '1997','1998','1999','2000','2001'

  4. Edit the "Other (Case Files)" selection statement to read:

    {Site and Morphology.Site recode} = 'Breast'

  5. Open the dictionary. Expand the "Race, Sex, Year Dx, Registry, County" folder and Create a new user-defined variable based on "Race recode A".

  6. Delete the "All races" and "Unknown" groupings, so that only the "White", "Black", and "Other" groupings remain.

  7. Give the variable a unique name (for example, "Race recode A [W/B/O]") and click OK. Close the dictionary.

  8. On the Table tab, open the "User-Defined" folder, click your variable's name, and click Row.

  9. Enter a title on the Output tab and execute the session.

  10. Consult the Rate Ratio column in your results matrix. Since "White" was the first grouping in your user-defined variable, a ratio will be displayed in the Rate Ratio column for the Black and Other rows, comparing the figure in those rows' Rate columns to the figure in the White row's Rate column. A footnote symbol in the Black/Rate or Other/Rate cells indicates that those rates are significantly different from the White rate.