10.What do you think would be a good way to avoid selection bias?

11.The concept of an iid is important when discussing sampling.In the material we've covered this week, when does the concept of an iid come into play?

12.Polly is doing a cluster sample; she plans to select 100 people from each cluster.Cluster A has 10,000 people.Cluster B has 40,000 people.Cluster C has 20,000 people.What sort of problems will occur?What are the ramifications?

please answer as sooon as possible!!!