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Monthly Sales Trend Forecasting
Linear regression on 12 months of steadily growing sales data to forecast next quarter. Demonstrates high R² (99.9%), validated assumptions, and extrapolation warnings with confidence intervals.
Input
What you provide to the skill
I have 12 months of monthly sales data (Jan: 50K, Feb: 52K, Mar: 55K, Apr: 58K, May: 61K, Jun: 64K, Jul: 67K, Aug: 70K, Sep: 72K, Oct: 75K, Nov: 78K, Dec: 81K). Forecast next 3 months.
Output
What the skill generates for you
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REGRESSION ANALYSIS RESULTS
DATA QUALITY
- Observations: 12 months
- Missing values: 0
- Sales range: $50K - $81K
- Mean sales: $65.2K
- Std deviation: $10.28K
- Correlation coefficient: 0.9996
- Sample size check: PASS (n=12)
- Variance check: PASS
- Quality gates: ALL PASSED
MODEL FIT
- R² = 0.9991 (explains 99.9% of variance)
- Adjusted R² = 0.9990
- F-statistic: 11412.80 (p = 0.000000)
- Slope: $2.850K per month (p = 0.000000)
- Intercept: $46.73K
Interpretation: Sales increase by $2.85K per month on average
ASSUMPTION CHECKS
- Linearity: OK (residuals centered near zero)
- Homoscedasticity: OK (Breusch-Pagan p = 0.2083)
- Normality: OK (Shapiro-Wilk p = 0.6911)
- Independence: OK (Durbin-Watson = 1.619)
2025 FORECASTS (Next 3 Months)
January 2025: $83.8K
95% Confidence Interval: $83.3K - $84.2K
95% Prediction Interval: $82.9K - $84.6K
February 2025: $86.6K
95% Confidence Interval: $86.1K - $87.1K
95% Prediction Interval: $85.8K - $87.5K
March 2025: $89.5K
95% Confidence Interval: $88.9K - $90.0K
95% Prediction Interval: $88.6K - $90.4K
EXTRAPOLATION WARNING
Forecasting 3 months beyond training data (months 1-12).
Predictions assume linear trend continues unchanged.
Uncertainty increases with forecast horizon.
BUSINESS RECOMMENDATIONS
- Model shows strong linear growth trend (R² = 99.91%)
- Expected monthly increase: $2.85K (very consistent)
- Use forecasts for planning with +/-15% contingency buffer
- Update model monthly as new data arrives to improve accuracy
- CORRELATION ≠ CAUSATION - model shows trend, not underlying drivers
- Consider external factors: seasonality, market conditions, competition
- Model assumptions are satisfied - forecasts are statistically valid
- Predicted Q1 2025 total: $259.9K
About This Skill
Build validated regression models for business forecasting with automatic assumption checking, diagnostic plots, confidence intervals, and extrapolation warnings.
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