Leigh's last comment on language precision and its efficacy is
important. ge oresebts no studies to show that his view is correct but
he is experienced enough that his impressions should be taken seriously.
A study to "prove" his statement would be costly in terms of
money and time. That situation pertains to many of the things we do.
Many people oppose a course of action by saying "do you have
anystudies showing that it works?" You should reply "do you have any
studies showling that it does not work?
Either do a study or take the best anecdotal evidence or impressions
available.