Question

“Prostate cancer patients treated by a new non-invasive method were significantly more likely to die within

the next five years compared to those patients who were treated by surgery.”

A). Identify the implied dependent and independent variables.

B). Does the headline demonstrate a positive or negative correlation between the two?

C). Is there a plausible mechanism (confounding factor) through which we could explain why the independent variable has a

causal impact on the outcome?

D). Now try to think of reasons why this could be a spurious relationship instead and construct alternative explanations.

Answer 1

A)Here,

The time(in years) after treatment is implied dependent variable

and the method of treatment is independent variable

B)

The headline demonstrates a negative correlation

Reason:-We consider non-invasive method to be improvement over surgery.So improvement in medical facility leads to decrease in lifetime

C)

We can broadly classify prostate cancer into four different stages from 1 to 4,with 4 being the most serious.these broad groups are based on much more detailed system that includes specific information about the tumour and how it affects the body.

So here stage of prostate cancer is the confounding factor

D)

Spurious is a term used to describe a statistical relationship between two variables that would, at first glance, appear to be causally related, but upon closer examination, only appear so by coincidence or due to the role of a third, intermediary variable. When this occurs, the two original variables are said to have a "spurious relationship."

We know cancer spreads by rapid cellular multiplication.In surgery ,the physical method of removing the tumour increases the chances in great extent rather than treating the can cells by drugs.In latter there are chances that all cancerous cells are not destroyed .

Hence the relation between the variables is spurious