Statistical Measure for Disease Case Calculation
The mean (option A) is the appropriate statistical measure to calculate the average number of disease cases over different time periods.
Rationale for Mean in Epidemiologic Surveillance
When an epidemiologist needs to determine "how many cases come" to a city over different time periods using 14 different numbers, they are seeking a measure of central tendency that represents the typical or average disease burden. The mean provides the arithmetic average that directly answers questions about average case counts across time periods 1.
- The CDC's Morbidity and Mortality Weekly Report consistently uses mean values (labeled as "Med" for median in their tables, but calculates means for 4-week totals) when comparing current disease case counts to historical averages 1.
- For disease surveillance and public health planning, the mean directly quantifies the expected number of cases, which is essential for resource allocation and outbreak detection 2, 3.
- The mean is the standard measure when calculating incidence rates and disease frequency in populations 2, 3, 4.
Why Other Options Are Inappropriate
Mode (option B) represents only the most frequently occurring value and would not provide meaningful information about average case counts across different time periods 5.
Median (option C) represents the 50th percentile and is more appropriate for skewed distributions or when describing incubation periods, not for calculating average case counts 6, 5.
Range (option D) describes only the spread between minimum and maximum values, providing no information about the typical or average number of cases 5, 7.
Epidemiologic Context
- Disease surveillance systems use mean values to establish baseline expectations and detect deviations that may indicate outbreaks 1.
- The mean allows direct comparison of current case counts to historical averages, which is fundamental to epidemiologic monitoring 1.
- Incidence calculations, which measure new disease occurrence over time, inherently rely on mean values to express average disease frequency 2, 3, 4, 7.