The variable is the group that was given caffine, because thats what the doctors manipulated. They possibly altered the natural memory of the participants by giving them caffine. A more specific variable could be how much caffine each participant is given and what time are they given it.
Answer:
No; she can still do the charge back
Explanation:
I believe she should've checked the tags before buying them and you don't need to remove the tag to check the fabric so the store has the right to say no returns but she can still do the charge back if the bank allows her
Answer:
can y write it in English? sorry I can't understand
They'er gnerally used as painkillers