Standard deviation

Question

Standing eye heights mean= 1634mm

Standard deviation=66mm

 

What standing eye height separates lower 95% from upper 5%

Answer 1

Obtain a z-score chart:

http://www.utdallas.edu/dept/abp/zscoretable.pdf

 

95% has a z-score of 1.641  (use interpolation)

 

z = (X - μ) / σ, X = data, μ = mean, σ = standard deviation

 

1.641 =(X - 1634) / 66          multiply both sides by 66

108.306 = X - 1634               add 1634 to both sides

1742 ≈ X

 

A standing height of 1742 mm separates the upper 95%.