A scientist has established

Yes, actually more back pain => less yoga on average


Kind of. More tendency to do yoga => less back pain on average. This study doesn't say this correlation holds for every individual, but for groups of individuals. Some might do yoga through the pain, some might skip yoga even though they are pain free, but on average, the correlation holds.

No it means less yoga. It doesn't mean none at all.




No. If A (more back pain) causes B (less yoga) it doesn't mean B causes A

But he asked: if not B then not A, if more yoga then less back pain. (Ok, he said no back pain which is not right, but it seems like he was going for the contrapositive.)

A scientist has established that the greater the incidence of chronic back pain a study participant reported, the less likely he or she was to practice yoga.

does that mean , great back pain = no yoga practised

It says that a scientist found in a study/studies that the more frequently people experienced chronic back pain, the less likely it was that that person would practice yoga.

It doesn't address the intensity of the pain, just the frequency; higher frequency of back pain = less involvement in the practice of yoga

if this is true , can we say more yoga = no back pain ?

The given information does not address this.