The average weekly earnings ofa production worker in 2000 were AUD426. Suppose a labor researcher wants to test to determine whether this gure is still accurate today. The researcher randomly selects 57 production workers and obtains a representative earnings statement for one week from each. The resulting sample average is AUD432.9. Assuming a population standard deviation of AU D341], and a 5% level of signicance, determine whether the mean weekly earnings of a production worker have changed. Determine the critical value 26 and z score value z based on the sample data. The critical value 2c : ' The z score value 2: based on the sample data 2