Consists of mc, calculations long and short and maybe a short answer, mc come directly from chapters at least 20 mc, calculations should be in class and homework, cheat sheet, mc in pen, z table given, Often times compare two or more samples. Detect significant differences not bc of chance or sampling error. One sample case we compare random sample to the pop, to see if different from pop, use sigma and t. Basically, often test null hypotheses, no difference between two samples. Any observed difference is due to sampling error. Null hyp is devils advocate, nothing going on. Obtain or reject null hyp, reject there is something going on results significant and potentiaaly true. Mu 1 = mu2 two samples against each other random testing pop means. The alt hypothesis is opposite of the null. Null rejected then research hypotheses, never test research hypotheses. Reject null accept research means there is a pop difference.