The management of Golding Company has determined that the cost to investigate a variance produced by its standard cost system ranges from $2,000 to $3,000. If a problem is discovered, the average benefit from taking corrective action usually out- weighs the cost of investigation. Past experience from the investigation of variances has revealed that corrective action is rarely needed for deviations within 8 percent of the standard cost. Golding produces a single product, which has the following standards for materials and labor:

Direct materials (8 Ib @ $0.25) $2 Direct labor (0.4 hr @ $7.50) 3 Actual production for the past three months with the associated actual usage and costs for materials and labor follow. There were no beginning or ending raw materials inventories.
April May June Production (units) 90,000 100,000 110,000 Direct materials:
Cost $189,000 $218,000 $230,000 Usage (Ib) 723,000 870,000 885,000 Direct labor:
Cost $270,000 $323,000 $360,000 Usage (hr) 36,000 44,000 46,000 Required:
1. What upper and lower control limits would you use for materials variances? for labor variances?
2. Compute the materials and labor variances for April, May, and June. Identify those that would require investigation.
3. Let the horizontal axis be time and the vertical axis be variances measured as a percentage deviation from standard. Draw horizontal lines that identify upper and lower control limits. Plot the labor and material variances for April, May, and June. Prepare a separate graph for each type of variance. Explain how you would use these graphs (called control charts) to assist your analysis of variances.