name the six types of bias that can come into effect while doing a study.

1. Selection bias--non random assignment to study group
2. Recall bias--knowledge of presence of disorder alters recall by subjects
3. Sampling bias--subjects are not representative; therefore results are generalizable
4. Late-look bias--information gathered at an inappropriate time
5. Lead-time bias
6. Confounding bias--the study groups were chosen from the same community r/t hypertensive agents; one group was placed on the drug (placebo) only and the other group was placed on the drug and diet; the blood pressure decreased but did it decrease because of the drug or the drug/diet or the diet. The groups are from the same community.. how we do know that some of the people did not talk to each other...???

Please post any follow-up questions with answers, and/or comments.. thank you.