D
(dyspnoea), a two-level factor with levels yes
and no
.
T
(tuberculosis), a two-level factor with levels
yes
and no
.
L
(lung cancer), a two-level factor with levels
yes
and no
.
B
(bronchitis), a two-level factor with levels
yes
and no
.
A
(visit to Asia), a two-level factor with levels
yes
and no
.
S
(smoking), a two-level factor with levels yes
and no
.
X
(chest X-ray), a two-level factor with levels
yes
and no
.
E
(tuberculosis versus lung cancer/bronchitis), a
two-level factor with levels yes
and no
.