Investigate Example Conduct i The Centers for Disease Control and Prevention (CDc) conducted a series of case-control studies in 1989 and 1990 a One of the studies conducted in minnesota. researchers selected 63 case subjects of eMs in the metropolitan area of Minneapolis-St Paul Researchers randomly selected 5188 control subjects in the same area Researchers interviewed subjects and asked abort potential risk factors and about their use ofL tryptophan
n The Centers for Disease Control and Prevention(CDC) conducted a series of case-control studies in 1989 and 1990. n One of the studies conducted in Minnesota, Researchers selected 63 case subjects of EMS in the metropolitan area of Minneapolis-St.Paul. n Researchers randomly selected 5188 control subjects in the same area. n Researchers interviewed subjects and asked abort potential risk factors and about their use of Ltryptophan. Investigate Example Conduct
Investigate Example Results L-tryptophan was taken significantly more frequently by cases than by controls--61 of 63 case subjects(97%),but only 101 of 5188 control subjects(2%) a L-Tryptophan-containing products were taken off the market in november 1989In 1990, after the recall of L-tryptophan, the number of reported cases fell to near zero
n L-tryptophan was taken significantly more frequently by cases than by controls— 61 of 63 case subjects (97%),but only 101 of 5188 control subjects (2%). n L-Tryptophan-containing products were taken off the market in November1989,In 1990,after the recall of L-tryptophan,the number of reported cases fell to near zero. Investigate Example Results
Design Selection of cases Develop a case definition then identify new cases within a specified time period a Selection of controls The sample of controls should have the same prevalence of exposure as the source population of unaffected persons a Determination of exposure EPIDEMIOLOGY AN EALTH STATISTI
n Selection of Cases Develop a case definition then identify new cases within a specified time period n Selection of Controls The sample of controls should have the same prevalence of exposure as the source population of unaffected persons. n Determination of Exposure Design EPIDEMIOLOGY AND HEALTH STATISTICS 1957 卫