At some point in time, most project managers have to implement corrective action to get a project back on track. EVM variance (SV, CV) and performance index (SPI, CPI) thresholds for corrective action are often specified in project cost and schedule management plans. As a project manager, preparing cost and schedule management plans, at what variance or performance index thresholds would you implement corrective action and why? Note: for the purposes of this topic, assume corrective action consists of proactive measures to get the project back on track.