Last Updated: November 21, 2025
Measures of Central Tendency
| Item | Description |
|---|---|
Mean
|
Average: sum / count |
Median
|
Middle value when sorted |
Mode
|
Most frequent value |
Measures of Spread
| Item | Description |
|---|---|
Range
|
Max - Min |
Variance
|
Average squared deviation |
Standard Deviation
|
√Variance |
IQR
|
Q3 - Q1 (middle 50%) |
Probability
P(A) = favorable / total
Basic probability
P(A and B) = P(A) × P(B)
Independent events
P(A or B) = P(A) + P(B) - P(A and B)
Union
Complement
P(not A) = 1 - P(A)
Hypothesis Testing
Null hypothesis (H₀)
No effect/difference
Alternative (H₁)
There is an effect
p-value
Probability of result if H₀ true
Significance level
Usually 0.05
Reject H₀
If p < 0.05
💡 Pro Tip:
Correlation does not imply causation!