### Warm-up Day of Ch. 7 Test

1. Which of the following are true statements about sampling?

I. Careful analysis of a given sample will indicate whether or not it is random.

II. Sampling error implies an error, possibly very small but still an error, on the part of the surveyor.

III. Data obtained when conducting a census are always more accurate than data obtained from a sample, no matter how careful the design of the sample survey.

(A) I only (B) II only (C) III only (D) None of the statements are true.

(E) None of the above gives the complete set of true responses.

2. Which of the following statements about residuals are true?

I. The mean of the residuals is always zero.

II. The regression line for a residual plot is a horizontal line.

III. The standard deviation of the residuals gives a measure of how the points in the scatterplot are spread around the regression line.

I and II (B) I and III (C) II and III (D) I, II, and III (E) None of the above.