So by using structured root cause analysis and hypothesis testing techniques, we can validate the findings and propose targeted corrective strategies.
In addition, we need to start by analyzing different sets of data to understand trends, timelines, forecast accuracy etc.
Data sources may include:
Sales Data (12 months): Seeking trends to indicate a mismatch between high-demand periods and stock availability leading to Lost Sales impact.
Inventory Records: For stock-out frequency of high-volume SKUs across the above period.
Forecast Accuracy Reports: To check for variance from actual demand.
Delivery Timeline Logs: For Supplier delivery windows. On-time delivery performance >95%, suggesting minimal impact from logistics delays.
Key Insights identified :
Forecast Error Correlation: High forecast inaccuracies coincide with stockout events, especially for promotions and new product launches.
Replenishment Lag: Time between forecast input and stock arrival often spans 10–14 days, reducing responsiveness.
Demand Volatility Ignored: Forecasts do not factor in localized demand surges, social trends, or weather-related events.
Inventory Turnover Analysis: Low turnover rates in some categories suggest misallocation of inventory resources.
Analysis Techniques Used
1. Process Mapping (SIPOC Analysis)
2. Root Cause Analysis - 5 Whys Technique
Problem: Products are frequently out of stock
3. Fishbone Diagram (Cause & Effect Analysis)
4. Hypothesis Testing
Test 2 primary hypotheses using statistical analysis:
Hypothesis 1: Delivery delays cause stockouts. We found out that on-time delivery has remained stable at > 95%, so we can confidently disprove this hypothesis. It's noise, not the cause.
Hypothesis 2: Poor forecasting drives stockouts. By mapping “Forecast accuracy %” against “stockout incidents” we can find out the correlation between them. With a significant p-value we have statistical proof that this is the primary driver.
How to Prevent Chasing the Wrong Cause -
Define the Problem with Data - Begin with a problem statement from the Measure phase (e.g., "From Q2 to Q4, stockouts on A-list items increased by 40%, contributing to an estimated $1.2M in lost sales."). This is our ultimate benchmark. If an identified "cause" doesn't statistically impact this metric, it's not the right one!
Gemba walk – Speaking with the store managers, the inventory planners, and the logistics coordinators is important as they have qualitative insights that can help with data analysis.
Use a combination of Tools: Using a combination of tools like the Fishbone Diagram provides the structure, the Regression Analysis provides the statistical proof, and the 5 Whys provide the deep dive.