1. A manufacturer receives parts from two suppliers. An SRS of 400 parts from supplier 1 finds 20 defective. An SRS of 100 parts from supplier 2 finds 10 defective. Let p1 and p2 be the proportion of all parts from suppliers 1 and 2, respectively, that are defective. The standard error needed to compute a 95% confidence interval for p1 - p2, the difference in the two proportions is
A. 0.001.
B. 0.063.
C. 0.032.
2. A noted psychic was tested for ESP. The psychic was presented with 400 cards face down and asked to determine if each card was marked with one of four symbols: a star, cross, circle, or square. The psychic was correct in 120 cases. Let p represent the probability that the psychic correctly identifies the symbol on the card in a random trial. Suppose you wish to see if there is evidence that the psychic was doing better than just guessing. To do this you test the hypotheses
H 0: p = 0.25,
H a: p > 0.25.
The P-value of your test is
A. 0.0104.
B. 0.0146.
C. 0.9896.
2. A manufacturer receives parts from two suppliers. An SRS of 400 parts from supplier 1 finds 20 defective. An SRS of 100 parts from supplier 2 finds 10 defective. Let p1 and p2 be the proportion of all parts from suppliers 1 and 2, respectively, that are defective. A 98% confidence interval for p1 - p2, the difference in the two proportions is
A. -0.05 ± 0.033.
B. -0.05 ± 0.068.
C. -0.05 ± 0.074.