Schedule Variance (SV)

Schedule Variance (SV) in Earned Value Management

What is Schedule Variance (SV)?

Schedule Variance (SV) is a critical metric in Earned Value Management (EVM) that measures project schedule performance by comparing the work completed against the work planned. It tells project managers whether a project is ahead of schedule, on schedule, or behind schedule.

The formula for Schedule Variance is:

SV = EV - PV

Where:
• EV (Earned Value) is the value of work actually completed
• PV (Planned Value) is the value of work scheduled to be completed

Interpreting Schedule Variance:

• Positive SV (SV > 0): Project is ahead of schedule
• Zero SV (SV = 0): Project is on schedule
• Negative SV (SV < 0): Project is behind schedule

Why Schedule Variance is Important

Schedule Variance provides several key benefits to project management:

1. Early Warning System: SV helps identify schedule slippages early, allowing for timely corrective actions

2. Quantitative Measurement: It provides an objective, monetary value to schedule performance rather than subjective assessments

3. Trend Analysis: Tracking SV over time reveals whether schedule performance is improving or deteriorating

4. Communication Tool: SV offers a clear, standardized way to communicate schedule status to stakeholders

5. Integration with Cost: Works alongside Cost Variance (CV) to give a complete picture of project health

How Schedule Variance Works in Practice

Let's consider an example:

A project task has a budget of $10,000 and is scheduled to be 50% complete by the status date. The actual work shows it's only 40% complete.

PV = $10,000 × 50% = $5,000
EV = $10,000 × 40% = $4,000
SV = $4,000 - $5,000 = -$1,000

The negative SV of $1,000 indicates the project is behind schedule, specifically by the equivalent of $1,000 worth of work.

Schedule Variance Percentage (SV%)

For easier comparison across projects, SV can be expressed as a percentage:

SV% = (SV ÷ PV) × 100%

In our example:
SV% = (-$1,000 ÷ $5,000) × 100% = -20%

This means the project is 20% behind schedule relative to what was planned.

Limitations of Schedule Variance

1. SV is expressed in monetary terms, not time units, which can sometimes be confusing

2. SV tends to converge to zero at project completion even if the project finished late

3. SV doesn't account for the critical path, so it may not reflect the true impact on project completion date

Schedule Performance Index (SPI)

SV is often used alongside Schedule Performance Index (SPI), which is calculated as:

SPI = EV ÷ PV

• SPI > 1: Ahead of schedule
• SPI = 1: On schedule
• SPI < 1: Behind schedule

For our example:
SPI = $4,000 ÷ $5,000 = 0.8

This indicates the project is progressing at 80% of the planned rate.

Exam Tips: Answering Questions on Schedule Variance (SV)

1. Memorize the Formula: Know that SV = EV - PV. Many exam questions require quick application of this formula.

2. Understand the Interpretation: Be clear about what positive, negative, and zero values mean for schedule performance.

3. Practice Calculations: Work through sample problems where you calculate SV from given EV and PV values.

4. Connect with Other Metrics: Understand how SV relates to SPI, CV, CPI, and other EVM metrics.

5. Remember Units: SV is always expressed in currency units (dollars, euros, etc.), not in time units.

6. Look for Trend Questions: Exams may ask about interpreting SV trends over the project lifecycle.

7. Watch for Scenarios: Some questions present a project scenario and ask you to determine if the project is ahead or behind schedule based on SV.

8. Consider Corrective Actions: Be prepared for questions about appropriate corrective actions based on SV results.

9. Distinguish from CV: Don't confuse Schedule Variance (SV) with Cost Variance (CV = EV - AC).

10. Cumulative vs. Period Values: Understand that SV can be calculated for a specific period or cumulatively for the project to date.

By mastering Schedule Variance calculations and interpretations, you'll be well-equipped to answer EVM questions on your PMI-SP or other project management certification exams.