Statistical Methods

Incidence and Death Rates

Ideally, crude, age-adjusted, and age-specific rates are used to plan for population-based cancer prevention and control interventions.

Confidence Intervals

Confidence intervals reflect the range of variation in estimating cancer rates. The width of a confidence interval depends on sample size, the amount of variability in the data, and confidence level. Narrow confidence intervals tend to imply greater certainty in the estimate, while wide confidence intervals tend to imply more variability in the data and could mean there is less certainty.

Stage at Diagnosis

Stage measures how far a cancer has spread from its origin. The staging system used by CDC’s National Program of Cancer Registries (NPCR) and the National Cancer Institute’s Surveillance, Epidemiology, and End Results (SEER) programs is called Summary Stage. Information on stage provided in the U.S. Cancer Statistics Data Visualizations tool is classified using a Merged Summary Stage variable that combines summary stage variables used during different time periods.

Relative Cancer Survival

Surveillance of cancer incidence and survival are essential in monitoring and understanding CDC’s efforts to support the needs of people who have cancer now or had cancer in the past.

Cancer Prevalence

Prevalence is the number of people with a specific disease or condition in a given population at a specific time. This measure includes both newly diagnosed and pre-existing cases of the disease. It is different from incidence, because incidence measures only the number of newly diagnosed cases in a given population at a specific time. Prevalence helps identify the level of disease burden on the population and health care system at a certain point in time. It is a function of both incidence and survival.

Screening, HPV Vaccination, and Risk Factor Prevalence Estimates

Healthy behaviors such as being physically active, avoiding tobacco, limiting the amount of alcohol you drink, and getting cancer screening tests and human papillomavirus vaccine when recommended may prevent or help manage cancer.

Risk Factor-Associated Cancers

Although cancer represents many heterogeneous diseases, some cancer types share common risk factors. Because risk factor information is not routinely collected by cancer registries, estimates for risk factor-associated cancers often are based only on cancer type. Using these standard definitions for risk factor-associated cancers can help facilitate comparisons of cancer burden across states and communities.

Incidence and Death Estimates by Congressional District

Cancer incidence and death rates and counts were estimated for federal congressional districts.

Suppression of Rates and Counts

Cell suppression is used to protect patient confidentiality. By using a threshold value of 16 for cell suppression, the risk of disclosing personally identifiable information is reduced. Cell suppression is also used when the numbers of cases or deaths used to compute rates are small, because those rates tend to have poor reliability. Frequencies and percentages are suppressed for groups with fewer than 16 cases. In addition, complementary cell suppression is done to suppress data for both sexes combined if data are suppressed for one sex.