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The normal distribution (bell curve) is the most common probability distribution in statistics. It's defined by mean μ and standard deviation σ, describing many natural phenomena.
Formel
f(x) = (1 / (σ√(2π))) × e^(-(x-μ)²/(2σ²))
Trinn-for-trinn guide
- 1Enter mean μ, standard deviation σ, and value x
- 2Calculate the z-score: (x - μ) / σ
- 3Look up cumulative probability or use the formula
Løste eksempler
Inndata
μ = 100, σ = 15, x = 115
Resultat
z = 1, P(Z ≤ 1) ≈ 0.841
Standard normal lookup
Vanlige feil å unngå
- ✕Confusing z-score with probability
- ✕Using population vs sample standard deviation
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