Question

(1 point) Sheila's measured glucose level one hour after a sugary drink varies according to the Normal distribution with μ μ = 130 mg/dl and σ σ = 20 mg/dl. What is the level L such that there is probability only 0.05 that the mean glucose level of 8 test results falls above L?

L=

L =

Answer 1

We are given

Now:

We need to find a score x so that the corresponding cumulative normal probability is equal to 0.95. Mathematically, x is such that:

The corresponding z score so that the cumulative standard normal probability distribution is 0.95 is

This value of zc​=1.6449 can be found either with Excel, or with a normal distribution table. Hence, the X score associated with the 0.95 cumulative probability is

Graphically:

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