Urn A has four red, three blue, and two green balls. Urn B has two red, three blue, and four green balls. A ball is drawn from urn A and put into urn B, and then a ball is drawn from urn B. a. What is the probability that a red ball is drawn from urn B? b. If a red ball is drawn from urn B, what is the probability that a red ball was drawn from urn A?

STAT 2004 Week 2 Lecture 5 Fri. 01/27/17 Observational study: data analysis where researcher does not interfere with data outcomes Experiment: researcher directly interferes with data outcomes y imposing treatments and controls Observational An example of an observational study would be a survey: did you get a flu shot Observational studies help establish correlation Experiment Randomly assign a treatment group (flu shot) and a control group (no flu shot) Help establish causation Sample frame: data has to be assigned with a number (a list of people, each have a number that doesn’t repeat) 194,147,134,33,62 Strata: (singular- stratum): subgroups or demographics of a population Stratified random sample: first break population into stra