What statistical measure is most appropriate for an epidemiologist to calculate the number of cases of a specific disease over different periods of time?

Statistical Measure for Disease Case Tracking Over Time

For tracking the number of disease cases over different time periods, the epidemiologist should calculate the mean (average) of the 14 values to determine the central tendency of case occurrence.

Rationale for Mean Selection

The mean is the most appropriate measure when an epidemiologist wants to calculate and understand the typical number of cases occurring across different time periods. 1 The mean provides:

• A single representative value that reflects the overall magnitude of disease occurrence across all measured time periods 2
• The foundation for calculating incidence rates, which are fundamental frequency measures in epidemiology that describe how disease is distributed in populations over time 2, 3
• Direct applicability to public health planning, as resource allocation and intervention strategies typically require understanding average case loads 4

Why Other Measures Are Less Appropriate

Mode (Option B)

• The mode identifies the most frequently occurring value but provides no information about the overall disease burden or typical case count 5
• In epidemiological surveillance with 14 different numbers, the mode may not even exist if all values are unique 5
• Mode is rarely used in epidemiological frequency measures for disease occurrence tracking 2, 4

Median (Option C)

• While the median is useful for skewed distributions or when outliers are present (such as incubation periods), it is less informative than the mean for calculating disease occurrence 5
• The median would be preferred only if extreme values were distorting the data, which is not indicated in this scenario 5
• Epidemiological frequency measures like incidence and prevalence calculations typically use mean values as the basis for rate computation 2, 4

Range (Option D)

• The range only describes the spread between minimum and maximum values without providing information about central tendency 5
• Range does not indicate the typical number of cases and cannot be used to calculate incidence or other epidemiological frequency measures 2, 4
• This measure provides no actionable information for understanding disease burden over time 6

Epidemiological Context

Frequency measures are fundamental in descriptive epidemiology and involve studying how disease is distributed in populations according to time, place, and person 2, 3 The mean number of cases across time periods allows calculation of:

• Incidence rates: the occurrence of new health outcomes during specific time periods 6, 4
• Average disease burden: essential for public health resource allocation 1
• Temporal trends: comparing mean values across different surveillance periods 1

The measurement of disease occurrence is one of the epidemiologist's most basic tasks, and the mean provides the most useful single summary statistic for this purpose when working with multiple time period observations 7, 4