Problem 10-26 The following is a control chart for the average number of minor errors in 22 service reports. UCL LCL a. Calculate the observed mean, expected mean, standard deviation and z value for the median and up/down test. (Negative amounts should be indicated by a minus sign. Round your answers to 2 decimal places.) Test Observed Expected Std. dev Z Median 8.00 0 12.00 2.29 - 1.75 Up/Down 11.00 14.33 1.89 -1.76