Augusto wants to prove to his parents that watching tv while he does his homework will him get better grades. he decides to ask 20 of his friends if they watch tv while they do their homework and what their grades are. he finds that his friends who have high grades also watch tv while they do their homework. he tells his parents that he has proven that watching tv while doing homework will cause his grades to improve. what mistake has augusto made?

he did not use a random sample, and he tried to show cause and effect with an observational study.

he did not use a random sample, and he tried to show cause and effect with an experiment.

he did not separate his friends into different groups, and he didn't apply a treatment.

he did not separate his friends into different groups, and he used a survey to collect data.