How could we figure out cause and effect for regarding a non experimental research of of kids that sit in the back of the class and the low grades they receive?

In teasing peers, what would be an operational definition for teasing?
Take a personality test on the Internet (you can find such tests using Internet search engines). Based on the information provided, what can you conclude about reliability, construct validity, and reactivity?
Can an unreliable test be valid? Explain your answer