The Leprosy data

Description

The leprosy data set was described in Scott and Wild (1997, 2001) and used as an example of standard two-phase case-control sampled data.

Usage

data(leprosy1)

Format

A data frame with 42 observations on the following 5 variables.

leprosy

a factor with levels no yes

age

a numeric vector indicating the mid-point of six 5-year age groups

scar

a factor with levels no yes

counts

a numeric vector indicating number of subjects with each observation

obstype

a factor with levels retro and strata, compulsory for function call

Details

The leprosy data were obtained by sampling from the results of a population cross-sectional study of people under 35 in Northern Malawi and represented as a three-way contingency table in Clayton and Hills (1993). Those people with leprosy were defined to be cases and the rest to be controls. The data were first categorized into six 5-year age sampling strata and the numbers of cases and controls falling into each stratum were observed. All cases have been chosen with an equal-sized control group subsampled from the control population within each age stratum. The potential risk factor that indicates the presence or absence of a BCG vaccination scar was then observed.

The data are represented in three different formats in leprosy1, leprosy2 and leprosy3. See "Description of the missreg Library" for more details.

References

Description of the missreg Library, Wild and Jiang, 2007

Examples

data(leprosy1)