SEER*Stat Trends Exercise 1b: Examine Trends in Rates
In exercise 1a we calculated trends for malignant breast cancer for females in the SEER 9 registries for the entire time period 1975-2011. By reviewing the rates in exercise 1a, it appears that there may be different trends. The rates are generally rising from 1975 until around 1999, then they begin declining for the remaining years. In this exercise, we will use SEER*Stat to calculate trends for two time periods, 1975-1999 and 2000-2011.
Is the APC for 2000-2011 significantly different from the APC for 1975-1999 (p < 0.05)?
Key Points and Reminders
Use the dictionary editor to create a variable called "Year of diagnosis (75-99, 00-11)". This variable should have 2 groupings, one for each of the time periods. Once this variable is created, it will appear as a choice in the Trend Variable control on the Statistic Tab.
SEER*Stat can test whether an APC over one time period significantly differs from an APC for a non-overlapping time period. The first time period defined in the trend variable is used as the base time period and each subsequent time period is compared to the base.
SEER*Stat cannot determine when the changes in trends occur. This is one of the main differences in SEER*Stat and the Joinpoint Trend Analysis Software (http://surveillance.cancer.gov/joinpoint/). Therefore, for this exercise we have pre-determined the two time periods.
SEER*Stat's export feature provides a method to create a generic ASCII text file containing the age-adjusted rates. This file can be used as the input data file in Joinpoint.
Step 1: Open Exercise 1a's Matrix and Retrieve the Session
SEER*Stat matrix files include the session information used to generate the table. This information serves as documentation for the results and provides a convenient method for generating similar statistics.
- Open your saved matrix file from exercise 1a. If you did not save the file, use the file key.trends1a.sim.
- Open the Matrix menu and choose Retrieve Session.
- Two windows should now be open in SEER*Stat. Close the Matrix window and begin working in the Rate Session window.
Step 2: Dictionary
- Use the , or select Dictionary from the File menu, to open the Dictionary.
- Open the "Race, Sex, Year Dx, Registry, County" folder, click on the "Year of Diagnosis" variable, then click Create.
- Name the new variable "Year of diagnosis (75-99, 00-11)".
- Delete all of the existing groupings.
- Highlight all of the values from 1975 to 1999 (inclusive) and click Add. Title the new grouping "1975-1999".
- To highlight a continuous range of values, click on the first value in the range, then hold down your SHIFT key while you click on the last value in the range.
- Highlight all of the values from 2000 to 2011 (inclusive) and click Add. Title the new grouping "2000-2011".
- Click OK to save the user-defined variable, then click Close to exit the Dictionary.
Step 3: Statistic Tab
On the Statistic tab:
- Change the Trend Variable to the "Year of Diagnosis (75-99, 00-11)" variable that you just created.
Step 4: Output Tab
On the Output tab:
- Edit the title of your matrix, if desired.
Step 5: Execute the Session
- Use the , or select Execute from the Session menu, to execute the session.
A dialog will display the progress of the job. When the job completes, a new window will open containing the output matrix.
Step 6: Check Your Results
- Compare your results to this SEER*Stat matrix file: key.trends1b.sim.