According to empirical rule, the area under the normal distribution or "bell-shaped curve", when plotted as a function of the z-parameter can be defined in terms of percentages.
The z-parameter (or z-score) is defined as
[tex]z= \frac{x- \mu }{ \sigma } [/tex]
where
x = value of random variable,
μ = the mean,
σ = standard deviation,
The total area under the curve = 1.
The curve below shows that within 2 standard deviations from the mean, the total area under the curve is 95% of the total area.
Answer: 95%
