VG2
statistikk
Quiz
What is the normal distribution?
The normal distribution is the most famous probability distribution — the characteristic bell curve that appears everywhere in nature.
The normal distribution describes many natural phenomena: height, weight, IQ, measurement errors. It is symmetric about the mean and has the famous bell-curve shape.
X ~ N(μ, σ²)
Where μ (mu) is the mean and σ (sigma) is the standard deviation.
The 68-95-99.7 rule
μ ± 1σ → 68% of values
μ ± 2σ → 95% of values
μ ± 3σ → 99.7% of values
μ ± 2σ → 95% of values
μ ± 3σ → 99.7% of values
Example: The height of Norwegian men is normally distributed with μ = 180 cm and σ = 7 cm.
68% are between 173 and 187 cm
95% are between 166 and 194 cm
68% are between 173 and 187 cm
95% are between 166 and 194 cm
Standard normal distribution
Z = (X - μ) / σ
Z tells us how many standard deviations a value is from the mean. Z ~ N(0, 1).
Nature loves the normal distribution — and the normal distribution loves nature.
— Carl Friedrich Gauss (1777–1855)
🧠 Test yourself
Question 1 of 5
What is the 68-95-99.7 rule?
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