Answer: 1.3
The more accurate value is 1.281551567
I rounded to the nearest tenth because of what the diagram tickmarks indicate.
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Step-by-step explanation:
The problem P(z > c) = 0.1 is equivalent to P(z < c) = 0.9
The invNorm function on a TI84 will find the value of c when we give an area to the left.
The template is
invNorm(area, mu, sigma)
where,
- mu = mean
- sigma = standard deviation
If we go for the much simpler template of
invNorm(area)
then we will use the default values mu = 0 and sigma = 1. This faster option is when we want a z-score.
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How to reach invNorm on a TI84?
Press the button labeled "2ND". Then press the "VARS" key.
Scroll down to invNorm which is the 3rd option.
Type in the following:
invNorm(0.9)
The result will be approximately 1.281551567
That rounds to roughly 1.3 when rounding to the nearest tenth. I'm rounding to one decimal place because of the tickmarks in the diagram.
So P(z < 1.3) = 0.9 and P(z > 1.3) = 0.1 approximately.
Therefore, you'll place the left endpoint at 1.3 and shade to the right.