Suppose X~N(22.8, 2.15) and P(x > 20)=.87
What is the z score
To find the z-score, we can use the formula:
z = (x - μ) / σ,
where x is the value being standardized, μ is the mean of the distribution, and σ is the standard deviation of the distribution.
In this case, x = 20, μ = 22.8, and σ = 2.15.
Plugging these values into the formula, we get:
z = (20 - 22.8) / 2.15
= -2.8 / 2.15
≈ -1.30
Therefore, the z-score is approximately -1.30.