Let A be an 8 5 matrix of rank 3, and let b be a nonzero vector in N(AT ). (a) Show that the system Ax = b must be inconsistent. (b) How many least squares solutions will the system Ax = b have? Explain.

What is Statistics Data collection: is collected by performing statistical experiment o 2 designs Controlled experiment Observational studies Ex. A new drug is discovered. How should an experiment be designed to test its effectiveness o We divide the subjects at random into two groups. One will receive the treatment and the other will not. The results will be compared. o The group that receive treatment is treatment group. o The group who do not receive the treatment is the control group. o The basic method to study the effectiveness of drug will be the method of comparison. o It should be double-blind; doctor don’t know which group the subjects are in and nei