>She didn't complete the full course, but has around 100-150 days of lessons
"Did wet streets cause rain or did rain cause wet streets" Did 100 lessons of treatment (duolingo) cause her to become proficient in English or are children with a natural proficiency towards language the ones that survive the treatment?
If only the strongest people survive having their blood drawn by leeches, it doesn't mean that leeches make you strong. Despite there being a high correlation in treatment outcome.
"Did wet streets cause rain or did rain cause wet streets" Did 100 lessons of treatment (duolingo) cause her to become proficient in English or are children with a natural proficiency towards language the ones that survive the treatment?
If only the strongest people survive having their blood drawn by leeches, it doesn't mean that leeches make you strong. Despite there being a high correlation in treatment outcome.