The impurity level (in ppm) is routinely measured in an intermediate chemical product. The following data were observed in a recent test:

2.4, 2.5, 1.7, 1.6, 1.9, 2.6, 1.3, 1.9, 2.0, 2.5, 2.6, 2.3, 2.0, 1.8, 1.3, 1.7, 2.0, 1.9, 2.3, 1.9, 2.4, 1.6 Can you claim that the median impurity level is less than 2.5 ppm?

(a) State and test the appropriate hypothesis using the sign test with 0.05. What is the P-value for this test?

(b) Use the normal approximation for the sign test to test versus . What is the P-value for this test?