DATA MANAGEMENT & STATISTICS

📊 DATA MANAGEMENT & STATISTICS REVIEWER

(Based on your handouts )

🧠 1. What is Data & Data Management?

🔹 What is Data?

• Data = raw facts or information

• Can be:

  • Qualitative → descriptions (e.g., color, opinions)

  • Quantitative → numbers (e.g., age, height)

👉 Example:

• “Blue” = qualitative

• “18 years old” = quantitative

🔹 What is Data Management?

Think of this as alaga system ng data mo.

• Organizing data

• Checking errors

• Preparing for analysis

• Storing & documenting data

💡 In short, ganito lang ‘yan:

🔥 Importance (Why it matters)

• Ensures accurate conclusions

• Makes data reusable (future studies)

• Improves efficiency & quality

🧠 Quick Memory Trick:

👉 D-A-T-A

• Data organized

• Analysis-ready

• Trustworthy

• Archived

📊 2. Methods of Data Collection

🔹 4 Main Methods:

💡 Key Insight:

• Census = complete but expensive

• Sampling = cheaper & faster

👉 Real-life:

🧠 Memory Trick:

👉 CS-E-O

• Census

• Sample

• Experiment

• Observation

🎯 3. Surveys & Sampling

🔹 Good Survey = Dapat ganito:

• Representative (fair sample)

• Random selection

• Neutral questions

• Controlled bias

💡 Example:
Bad question ❌: “Do you agree this product is amazing?”
Good question ✅: “How would you rate this product?”

🔹 Sampling Methods

🔴 Non-Probability Sampling

• NOT random

• Biased

Examples:

• Convenience sampling

• Quota sampling

👉 Example:

🟢 Probability Sampling (Better 🔥)

1. Simple Random Sampling (SRS)

• Equal chance lahat

2. Systematic Sampling

• Every nth item (e.g., every 10th person)

3. Stratified Sampling

• Divide into groups (e.g., male/female)

4. Cluster Sampling

• Group by location (e.g., barangay)

5. Matched Sampling

• Paired comparison (before vs after)

🧠 Memory Trick:

👉 “Si Syempre Study Classes Mo”

• Simple

• Systematic

• Stratified

• Cluster

• Matched

🧪 4. Experiments (Super Important 🔥)

🔹 Key Components

• Control Group → walang treatment

• Experimental Group → may treatment

• Random Assignment → fair distribution

• Replication → repeat for accuracy

💡 Real-life Example:

• Testing new skincare:

  • Group A: gumagamit

  • Group B: hindi

⚠ Bias & Errors

🔸 Confounding Variable

• Hidden factor affecting results

👉 Example:
Ice cream sales ↑ and drowning ↑
➡ Real cause: summer (confounder)

🔸 Placebo Effect

• Fake treatment but may effect pa rin

🔸 Blinding

• Participants don’t know treatment

🔸 Blocking

• Group similar subjects

👉 Example:
Separate males & females in study

🧠 Memory Trick:

👉 CPBB

• Confounding

• Placebo

• Blinding

• Blocking

🧪 5. Experimental Designs

💡 In short:

• Random = simple

• Block = organized

• Matched = paired

📈 6. Chi-Square Test (Very Exam Favorite 🔥)

🔹 Purpose:

To check if:

• Data matches expectation OR

• Two variables are related

🔹 Formula

χ2=∑(O−E)2E\chi^2 = \sum \frac{(O - E)^2}{E}χ2=∑E(O−E)2​

Where:

• O = Observed

• E = Expected

🔹 Types of Chi-Square

1. Goodness of Fit

👉 Checks if data matches expected distribution

2. Test of Independence

👉 Checks if 2 variables are related

🧠 Key Idea:

• Small χ² → good fit (may relationship)

• Large χ² → poor fit (no match)

🔹 Assumptions

• Random sample

• Independent observations

• Expected ≥ 5

🔹 Hypothesis

🔥 Example Insight (from your handout)

👉 On page 6–7,

• If χ² > critical value → Reject H₀

• Meaning: may difference or relationship

🧠 Memory Trick:

👉 “O-E squared over E”
(Just memorize flow ng formula)

📊 7. Chi-Square Table (Handout 2)

• Used to find critical value

• Based on:

  • Degrees of freedom (df)

  • Significance level (α)

👉 Makikita ito sa table (page 1 of Handout 2)

💡 Example:

• df = 3, α = 0.05 → critical = 7.815

🧠 Quick Tip:

👉 If computed χ² > table value → Reject H₀

⚡ FINAL RECAP (Ultra Simplified)

👉 If cram mode ka na, eto na lang tandaan mo:

🧠 Data Management

• Organize → Clean → Analyze → Store

📊 Sampling

• Random = good

• Non-random = biased

🧪 Experiments

• Control vs Experimental

• Watch out for bias

📈 Chi-Square

• Compare Observed vs Expected

• Big value = reject

🧠 ULTIMATE MEMORY HACK (EXAM READY)

👉 “D-S-S-E-C”

• Data Management

• Sampling

• Surveys

• Experiments

• Chi-square