The McMillan Newspaper Company sometimes makes printing errors in its advertising and is forced to provide corrected advertising in the next issue of the paper. The managing editor has done a study of this problem and found the following data:

No. of Errors x Relative Frequency 0 0.56 1 0.21 2 0.13 3 0.07 4 0.03

a. Using the relative frequencies as probabilities, what is the expected number of errors? Interpret what this value means to the managing editor.

b. Compute the variance and standard deviation for the number of errors and explain what these values measure.