Space-Time Scan Statistic

The Space-Time Scan Statistic detects clusters of unusually high, or unusually low, rates in space, in time, or in both together. The method scans a moving window across your study area and time period, comparing the cases and population observed inside each window against what would be expected by chance.

Study Period and Scan Direction

Set the period a scan covers with a slider, and choose whether to scan for unusually high values, unusually low values, or both. Cases and population are combined across whichever period you choose.

Outbreak Data

The Space-Time Scan Statistic works from case-event data, referred to in Vesta as outbreaks. Each outbreak is placed at a location — matched by location first, falling back to a name match — and carries its own case count.

Results

Detected clusters report their location, radius (in meters), and time span, alongside a measure of statistical significance.

Process Steps

  1. Click on the "Analyze" button from the side bar menu.
  2. Select "Space-Time Scan Statistic" from the available methods.
  3. Choose Automatic, Guided, or Full control guidance. See Analysis Introduction for more on the Guided Analyze wizard.
  4. Select the dataset containing your case (outbreak) data.
  5. Set the study period and scan direction.
  6. Select "Run" to scan for clusters.
  7. Detected clusters, along with their location, radius, span, and significance, are saved in the Data panel to the right.