Which of the following statements about observational studies is true? A census is always preferable to a sample survey since it
includes the entire population. II. A neutral designer of a survey who has no conscious predisposition toward any particular conclusion can still produce biased data. III. Statistical inference is not necessary when a census is conducted properly. (A) I only (B) II only (C) I and II (D) I and III (E) II and III I.
