Lawson & Waller's Score Test |
|
|
|
| Indications/Recommendations for use: Detects a decreasing trend in disease frequency associated with declining exposure to a point-focus. | |||
| Description: At each region, the difference between observed case counts and those expected under a Poisson distribution with a common rate is weighted by the degree of exposure to the focus. | |||
| Test statistic: Expectation of the test statistic is zero under the Null Hypothesis. |
|
||
| Null Hypothesis: The observed number of cases in each region are independent, Poisson random variables with a common rate. | Ho: | ||
| Alternative Hypothesis: The observed number of cases in each region are independent, Poisson random variables where the rate is a proportionally increasing function of exposure. | Ha: | ||
| GeoMed Inputs: Region-level data with a centroid coordinate, case counts, and population-at-risk per region; point-focus coordinate. | |||
| GeoMed Outputs: Test statistic and p-value. | |||
| Example Analysis |
Reference:
Lawson, A.B. 1989. Score tests for detection of spatial trend in morbidity data, Dundee Institute of Technology: Dundee. Waller, L.A., et. al. 1992. Chronic disease surveillance and testing of clustering of disease and exposure: Applicaiton to leukemia incidence and TCE-contaminated dumpsites in upstate New York, Envirometrics, 3(3):281-300. |
||