There is a bag with only red marbles and blue marbles. The probability of randomly choosing a red marble is

5

8

.

There are 56 marbles in total in the bag and each is equally likely to be chosen.

Work out how many red marbles there must be.

17. a researcher measures three variables, x, y, and z for each individual in a sample of n = 20. the pearson correlations for this sample are rxy = 0.6, rxz = 0.4, and ryz = 0.7. a. find the partial correlation between x and y, holding z constant. b. find the partial correlation between x and z, holding y constant. (hint: simply switch the labels for the variables y and z to correspond with the labels in the equation.) gravetter, frederick j. statistics for the behavioral sciences (p. 526). cengage learning. kindle edition.