Answer:
Explanation:
Given that in a study by Swedish researchers (Occupational and Environmental Medicine 2002;59:517-522), 2410 women who had worked as hairdressers and given birth to children were compared to 3462 women from the general populations who had given birth.
The hairdressers had a slightly higher percentage of infants with a birth defect.
a) Explanatory variable is the Hairdresser status
b) Response variable is Birth defect status.
c) Observational study because actually by nature what happened is recorded. No effort was taken to change or influence any variable here.
d) Income level in terms of salary is numerical and health benefits in terms of amount is numerical.