Epidemiology for the uninitiated. Observer variation.

Epidemiology for the uninitiated. Rates.

Rates are the hallmark of epidemiology, for they form the basis of comparisons between population groups. "Floating numerators" are anathema, for they cannot be interpreted. A choice of denominators Most rates take the form: Frequency of observed state or event Total No in whom this state or event might occur The denominator consists of all those, and only those, who might appear in the numerat...

Epidemiology for the uninitiated. Screening.

1417 and other dangerous substances may be taken unwittingly even in cold and cough remedies. A mandatory warning symbol such as a steering wheel, as suggested by Havard,3 would be helpful on both prescription and over-the-counter preparations. Drug abuse Evidence about the accident risk associated with drug abuse is sparse. Hard-drug takers are underrepresented in accidents, presumably because...

Epidemiology for the uninitiated. Comparing rates.

"Is this disease increasing ? Does it occur with undue frequency in my local community? Does its incidence correlate with some hypothesised cause ? Has the outcome changed since control measures were instituted ?" To answer such questions means setting two sets of rates side by side and making some sense of the comparison. This article will examine some of the problems which may arise. Terminol...

Epidemiology for the uninitiated. Experimental studies.

Epidemiology for the uninitiated. Aetiology--comparison between communities.