Label following study as either an observational study, an experiment, or neither.

Many parents have expressed concerns that pertussis vaccinations will cause wheezing disorders or asthma in later life. In 2009 the Journal of the American Academy of Pediatrics published research by the Institute of Social and Preventive Medicine in Bern, Switzerland. The researchers wanted to determine if routine childhood vaccination against pertussis (whooping cough) was associated with subsequent development of childhood wheezing disorders and asthma. The researchers studied 6811 children from the general population born between 1993 and 1997 in Leicestershire, UK. From birth through 2003, they conducted repeated questionnaire surveys about wheeze and asthma and then linked the respiratory symptom data to independently collected vaccination data from the National Health Service database. Then the researchers compared wheeze and asthma incidents for children of three different levels of vaccination (complete, partial, and no vaccination). The analyses were based on 6,048 children with available vaccination records.

a. observational study
b. an experiment
c. neither

An observational study is one in which the researcher seeks to discover the effect of a disease or treatment without interference on those who are affected or not affected by it. Observational studies could be of two types namely; the case-control, and the cohort study. The research given above is a cohort study because it compares a group of people born in the same time period and checks for the presence of a disease that could be linked to the vaccinations administered at birth.

A case-control study compares those affected by the disease to those not affected by it. An experimental study assigns the participants to groups and there is a control or placebo group. After this, the results from the groups are compared.