Risk refers to the chances that something bad might happen.
Minimal risk refers to a drug that has already been tested in previous research and found to have no bad reactions. YOu are asked to try the drug as part of a larger study to assess the risks of rare side-effects.
Low risk refers to a drug that has already been tested in a small sample, but some of those participants had allergic reactions. In such cases, it might be possible that there would be a serious reaction in a few people, but this is not likely.
Risky refers to a drug that has been tested in a number of studies. A few test patients died during the testing, which might have been due to their disease or possibly to the drug. You are warned that the deaths may have been due to side-effects of medication.
Very risky is a drug that definitely produced serious side effects. The drug company insists that these were due to impurities in the materials tested, but some scientists believe that the drug is too risky for testing. You are warned that the previous testing resulted in kidney failure and liver damage, and a few of the participants died as a result of these complications.
Payment refers to how much you are paid for participation. This is either
$50, $500, $1,000, $5,000, or $10,000.