|
HTDS Guide > How the Study
Was Conducted > How Data Were Analyzed
HTDS Guide
| How the Study Was Conducted |
 |
|
|
|
|
How Data Were Analyzed
In analyzing the data, researchers looked for what is called a
"dose-response." A dose-response is when risk of disease increases with
increasing dose of radiation. If a study finds a dose-response, it
provides very strong evidence linking radiation to the disease.
In the case of the HTDS, researchers studied how rates of thyroid
disease in the study group varied in relation to participants' radiation
doses from Hanford's iodine-131. The HTDS is an "internally controlled
study." This approach enables researchers to compare groups of people
who have similar characteristics (such as age, diet, lifestyle or
environment) but different levels of exposure.
This approach of using one population composed of individuals with
different levels of exposure has been used extensively in assessing the
effects of radiation exposure in human populations.
A less effective approach would be to compare the study group to a
separate population presumed to be unexposed to radiation ("unexposed
control group"). That approach would be less desirable because thyroid
disease may be a function of a number of factors other than exposure to
radiation, and those factors may differ considerably between different
populations.
Had the HTDS used an unexposed control group from another part of the
country, scientists could not have known whether any differences in the
rates of disease between the groups were due to a difference in exposure
levels or some other factor.
 Back
to Top Next: Consideration
of Other Sources of Radiation >>
|
