You should always check the quality and quantity of the evidence before forming an opinion.
You should also review your evidence before you perform an opinion.
To evaluate your own and other peoples opinions you will need to understand the various kinds of evidence.
This entails knowing the value and limitations of each kind, as well as the appropriate questions to ask.
*good studies have limitations listed
Unpublished reports are stories we hear from people hearsay gossip or on the internet the biggest limitation problem is that it is often difficult to confirm them.
To evaluate an unpublished report ask:
Where did the story originate ?
How can I confirm that the version I heard is the correct one ?
This kind of evidence exists in a wide variety of published or broadcasted works such as scholarly books, professional journals, newspaper articles, news broadcasts and or radio/TV commentaries
To evaluate a published report ask:
Does the report cite the sources of all important items of information?
Does the author broadcaster have a reputation for careful reporting?
Celebrities are increasingly seen endorsing product and services in commercials and infomercials.
To evaluate a celebrity testimonial
Is the celebrity a paid spokesperson?