A study was conducted in a particular place,to determine the
effects of vitamin A deficiency in preschool children.The
investigators were particularly interested in whether children with
vitamin A deficiency were at increased risk of developing
respiratory infection,which normally causes death.
250 children were recruited in the study,and their age in
years,gender(0=male,1=female),and whether they suffered vitamin A
deficiency (0=no,1=yes) was recorded at an initial clinic visit
(time 0).Also recorded was the response,whether the child was
suffering from a respiratory infection (0=no,1=yes)....