Statistics & Probability5 min read
Expected Value: Weigh Outcomes by Likelihood
Expected value multiplies each outcome by its probability and adds them up. A launch with 30%, 50% and 20% outcomes is worth ₹17,100 on average.
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22 articles
- Statistics & Probability4 min read
Geometric Mean for Growth Rates and Ratios
Take the nth root of the product of n values. Yearly factors of 1.10, 0.95 and 1.20 average 7.8% a year, not the 8.3% that simple averaging gives.
- Statistics & Probability4 min read
Average Speed for a Round Trip: Harmonic Mean Method
Drive 120 km out at 40 km/h and back at 60 km/h and your average is 48 km/h, not 50. The harmonic mean 2ab/(a+b) handles equal distances at different speeds.
- Statistics & Probability4 min read
Linear Regression: Finding the Best-Fit Line by Hand
Least squares gives the line y = a + bx through your points. Five study-hours and marks pairs yield y = 41.08 + 5.10x with r² of 0.988. Steps inside.
- Statistics & Probability4 min read
Margin of Error: Why a 1,000-Person Poll Is ±3.1 Points
For a proportion, margin of error is z × √(p(1−p)/n). With n = 1,000 and p = 50 percent at 95 percent confidence it is ±3.1 points. Steps and traps.
- Statistics & Probability5 min read
Odds to Probability: Convert 3:1, 2.5 and More
Odds of 3 to 1 against are a 25% chance, 3 to 2 in favour is 60%, and decimal 2.50 is 40%. Convert any odds format with one short rule.
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