Suppose we want to choose 3 letters, without replacement, from the 4 letters a, b, c, and d. (a) how many ways can this be done, if the order of the choices matters? (b) how many ways can this be done, if the order of the choices does not matter?

Harold took five different samples of thirty-five randomly selected students from the 520 students he surveyed. the means of the samples are shown below. sample mean sample 1: 3.4 sample 2: 3.2 sample 3: 4.1 sample 4: 4.6 sample 5: 3.1 the predicted mean of the population will fall between 3.1 and ?