collerating risk factors Flashcards
what did scientists do to try work out what was causing an increase of patients with lung cancer
observed people’s lifestyle habits to see if they could link any of these with lung cancer
what is epidemiology
studying the patterns of disease to determine risk factors
what did scientists notice
what did they observe
why did they do this
they notices that lung cancer was much more common among cigarette smokers than among non smokers.
They observed how many cigarettes people smoked each day and then how many of these people developed lung cancer
to see if there was a colleration between lung cancer and smoking
how did scientist determine whether there was a colleration between the risks (smoking) and disease(lung cancer)
what was this type of colleration called
They used a scatter graph
as the numbers of cigarettes smoked per day increases, the risk of developing lung cancer also increased
this is called a positive colleration graph
the colleration does not prove the cause but suggests that they might be linked
scientists had drawn another scatter graph with the number of years people smoked and the risk of developing lung cancer
the graph also had another positive colleration, what did scientist then do and discover?
began to look at how smoking could cause cancer (a scientific explanation)
scientists discovered that cigarette smoke contains chemicals which damage DNA and increase the risk of cancer
these are called carcinogens
what are carcinogens
a substance/agent that is capable of causing cancer
why do we now accept that smoking causes lung cancer?
scientists had a strong colleration between smoking cigarettes and lung cancer and they had a cause of mechanism
what is sampling
scientists sample a group of random people and then draw conclusions about the whole population.
why can taking a sample of a group in the same town not be good?
what do we do to avoid bias
it would be biased as for eg people in the town might take less exercise than average or might be exposed to a certain pollution in that town
to avoid bias we need to take as large a sample as possible and it must be as random as possible
we simply cannot take conclusions from a small or non-random sample
