Lesson · Hinglish · ⏱ 7 min padhne mein
📊 Average aur spread: mean, median, variance
EnglishHinglish
🏠 Asli zindagi ki misaal
Nau dost ₹30,000 mahina kamaate hain aur ek ₹10 lakh. 'Average' (mean) salary ₹1.2 lakh se upar aati hai, jo kisi ki bhi nahi hai! Median, yaani beech wale insaan ki salary, ₹30,000 hai, aur asli kahani yahi batati hai. Aur 'spread' poochta hai ki sab lagbhag same kamaate hain, ya numbers idhar-udhar bikhre hue hain.
💡 Aasaan shabdon mein
Modelling se pehle data ko describe karte hain. Mean = sum ÷ count, aur yeh extreme values (outliers) ki wajah se kheench jaata hai. Median sort karne ke baad beech wali value hai, aur outliers se zyaada farak nahi padta. Mode sabse common value hai. Spread batata hai ki numbers kitne bikhre hue hain: variance mean se average squared doori hai, aur standard deviation uska square root hai, data ki units mein hi. Hamesha centre aur spread dono check karo.
🎬 Dekho kaise kaam karta hai
Nau salaries ₹30k pe hain. Jab ek ₹10 lakh ki salary aati hai, mean ₹127k pe kood jaata hai, lekin median ₹30k pe hi rehta hai.
🪜 Step by step
- Mean: saari values jodo aur ginti se divide karo. Heights jaise symmetric data ke liye accha.
- Median: values sort karo aur beech wali lo. Jab extreme values hon, jaise salaries ya ghar ki keemat, tab use karo.
- Spread: range (max minus min) jaldi milta hai par sensitive hai. Standard deviation batata hai values aam taur par mean se kitni door hain.
- Percentiles: 90th percentile woh value hai jiske neeche 90% data hai. Delivery time ya API latency (p90, p99) jaisi cheezon ke liye use hota hai.
- Hamesha histogram banao: do datasets ka mean same ho sakta hai par shape bilkul alag.
🔑 Zaroori shabd
- Mean
- Normal average: sum ÷ count.
- Median
- Sort karne ke baad beech wali value. Outliers se dhokha nahi khaati.
- Standard deviation
- Values ki mean se typical doori.
👀 Example dekho
import statistics as st
salaries = [30, 30, 30, 30, 30, 30, 30, 30, 30, 1000] # in ₹ thousand
print(st.mean(salaries)) # 127.0 ← misleading
print(st.median(salaries)) # 30.0 ← the real picture
print(round(st.stdev(salaries), 1)) # 306.7 ← huge spreadEk outlier mean ko bahut badal deta hai, lekin median ko lagbhag nahi hilaata.
⚠️ Aam galtiyaan jinse bachna hai
- Sirf average batana. 'Average delivery 2 din' yeh chhupa deta hai ki 10% orders ek hafta lete hain.
- Income jaise skewed data ke liye mean use karna. Kuch bahut badi values use upar kheench leti hain; median zyaada sachcha hai.
✅ Jaldi se check karo
City ke house prices mein kuch bahut mehenge villas bhi hain. Typical ghar ko kaun better describe karega?
- Mean
- Median
- Maximum
Jawaab dekho
B. Median: Kuch villas mean ko upar kheench dete hain. Median beech wale ghar pe hi rehta hai.
🙋 Seekhne wale yeh poochhte hain
Variance aur standard deviation mein kya fark hai?
Standard deviation variance ka square root hai. Yeh data ki units (rupees, seconds) mein hota hai, isliye samajhna aasaan hai.
Tech teams p99 latency ki baat kyun karti hain?
Kyunki average un slow cases ko chhupa deta hai jo users ko mehsoos hote hain. p99 matlab 99% requests isse tez hain; sabse slow 1% aksar naraaz users ke liye sabse zaroori hote hain.
📌 Yaad rakho
Outliers hon to median use karo, aur spread bhi hamesha dekho.
Poora course, aapke roadmap ke hisaab se
Progress tracking, quick checks aur step-by-step order ke saath. Yeh lesson in courses ka hissa hai:
Course mein seekho