lightbulb Key Concepts

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1. Characteristics of Normal Distribution

• Bell-shaped and symmetrical about the mean.
• Mean = Median = Mode.
• The total area under the curve is 1.

2. Empirical Rule

• ~68% within 1 standard deviation.
• ~95% within 2 standard deviations.
• ~99.7% within 3 standard deviations.

3. Standard Normal Variable (Z)

Z = (X - μ) / σ

where μ is the mean and σ is the standard deviation.