(1) Small and arguably non-random sample size
(2) They proved correlation but not causation
(3) There's also a legitimate chicken-egg argument
(4) Survey was subjective and probably can't be replicated
(5) Multiple uncontrolled factors
I can go on, but you get the idea...
(1) Small and arguably non-random sample size
(2) They proved correlation but not causation
(3) There's also a legitimate chicken-egg argument
(4) Survey was subjective and probably can't be replicated
(5) Multiple uncontrolled factors
I can go on, but you get the idea...