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Normal loss density and interval probability

A continuous normal curve’s height is not the probability of an exact loss value.

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Separate a point from an interval

For a continuous normal loss law with positive dispersion, probability at a single specified loss is zero. The density at that point can still be positive. Probabilities arise by integrating the density across an interval.

Read the standard normal scale

The standard normal density at z=0 is about 0.398942 per z unit. That number does not mean a 39.8942% probability of exactly zero. The area over the whole real line is one.

Retain the density unit

Different graph quantities
QuantityUnit or meaning
Loss xOriginal loss units
Loss density fL(x)Probability per loss unit
Standardized zDimensionless standardized loss
Standard density φ(z)Probability per z unit
Interval areaDimensionless probability

Read the calculator’s plotted curve

The tool plots standard normal density against z. It does not show a discrete probability bar at each sampled point. Sampling more curve coordinates would improve a visual approximation, not create additional probability mass.

Further references