Which expression gives the probability density function f(z) of the standard normal distribution?
Correct answer C. 1/(σ√2π) e^(-1/2 z²)
Explanation
The standard normal density is f(z) = (1/√(2π)) e^(-z²/2); with σ = 1 the leading factor 1/(σ√(2π)) reduces to 1/√(2π), and the exponent must be negative so the curve falls away from zero.
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