Data Engineers

Data-Driven Decision Making

Data-driven decision-making (DDDM) involves using data analytics to guide business strategies instead of relying on intuition. Key techniques include A/B testing, forecasting, trend analysis, and KPI evaluation.

1️⃣ A/B Testing & Hypothesis Testing

A/B testing compares two versions of a product, marketing campaign, or website feature to determine which performs better.

✔ Key Metrics in A/B Testing:

Conversion Rate

Click-Through Rate (CTR)

Revenue per User

✔ Steps in A/B Testing:

1. Define the hypothesis (e.g., "Changing the CTA button color will increase clicks").

2. Split users into Group A (control) and Group B (test).

3. Analyze differences using statistical tests.

✔ SQL for A/B Testing:

Calculate average purchase per user in two test groups

SELECT test_group, AVG(purchase_amount) AS avg_purchase  
FROM ab_test_results  
GROUP BY test_group;

Run a t-test to check statistical significance (Python)

from scipy.stats import ttest_ind
t_stat, p_value = ttest_ind(group_A['conversion_rate'], group_B['conversion_rate'])
print(f"T-statistic: {t_stat}, P-value: {p_value}")

🔹 P-value < 0.05 → Statistically significant difference.
🔹 P-value > 0.05 → No strong evidence of difference.

2️⃣ Forecasting & Trend Analysis

Forecasting predicts future trends based on historical data.

✔ Time Series Analysis Techniques:

Moving Averages (smooth trends)

Exponential Smoothing (weights recent data more)

ARIMA Models (AutoRegressive Integrated Moving Average)

✔ SQL for Moving Averages:

7-day moving average of sales

SELECT order_date,  
       sales,  
       AVG(sales) OVER (ORDER BY order_date ROWS BETWEEN 6 PRECEDING AND CURRENT ROW) AS moving_avg  
FROM sales_data;

✔ Python for Forecasting (Using Prophet)

from fbprophet import Prophet
model = Prophet()
model.fit(df)
future = model.make_future_dataframe(periods=30)
forecast = model.predict(future)
model.plot(forecast)

3️⃣ KPI & Metrics Analysis

KPIs (Key Performance Indicators) measure business performance.

✔ Common Business KPIs:

Revenue Growth Rate → (Current Revenue - Previous Revenue) / Previous Revenue

Customer Retention Rate → Customers at End / Customers at Start

Churn Rate → % of customers lost over time

Net Promoter Score (NPS) → Measures customer satisfaction

✔ SQL for KPI Analysis:

Calculate Monthly Revenue Growth

SELECT month,  
       revenue,  
       LAG(revenue) OVER (ORDER BY month) AS prev_month_revenue,  
       (revenue - prev_month_revenue) / prev_month_revenue * 100 AS growth_rate  
FROM revenue_data;

✔ Python for KPI Dashboard (Using Matplotlib)

import matplotlib.pyplot as plt
plt.plot(df['month'], df['revenue_growth'], marker='o')
plt.title('Monthly Revenue Growth')
plt.xlabel('Month')
plt.ylabel('Growth Rate (%)')
plt.show()

4️⃣ Real-Life Use Cases of Data-Driven Decisions

📌 E-commerce: Optimize pricing based on customer demand trends.
📌 Finance: Predict stock prices using time series forecasting.
📌 Marketing: Improve email campaign conversion rates with A/B testing.
📌 Healthcare: Identify disease patterns using predictive analytics.

Mini Task for You: Write an SQL query to calculate the customer churn rate for a subscription-based company.

Data Analyst Roadmap: 👇
https://t.iss.one/sqlspecialist/1159

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