An English teacher was interested in studying the length of words in Shakespeare's MacBeth. She took a random sample of 300 words from MacBeth and wrote down the length of each word. She found that the average lexigth of words in that sample was 3.4 letters. What would be the parameter? a. number of words in the sample b. 3.4 c. average number of letters per word in the entire play of MacBeth d. all words in the play