Solved on Mar 12, 2024

Find the zz-score where the area to its right under the standard normal distribution is 0.39. Round the answer to 4 decimal places.

STEP 1

Assumptions
1. The standard normal distribution is symmetric about the mean, which is 0.
2. The total area under the standard normal distribution curve is 1.
3. The z\mathrm{z}-score is the number of standard deviations a data point is from the mean.
4. The area to the right of the z\mathrm{z}-score under the standard normal distribution is given as 0.39.
5. We are looking for the z\mathrm{z}-score such that the area to the left of it is 10.39=0.611 - 0.39 = 0.61.

STEP 2

To find the z\mathrm{z}-score corresponding to a given area to the left, we use the inverse of the standard normal cumulative distribution function (CDF), often denoted as Φ1(area)\Phi^{-1}(area).
z=Φ1(areatotheleft)\mathrm{z} = \Phi^{-1}(area\, to\, the\, left)

STEP 3

Calculate the area to the left of the z\mathrm{z}-score, which is 10.391 - 0.39.
areatotheleft=10.39=0.61area\, to\, the\, left = 1 - 0.39 = 0.61

STEP 4

Use a standard normal distribution table, calculator, or statistical software to find the z\mathrm{z}-score that corresponds to the area to the left of 0.61.
If using a table, we look for the value closest to 0.61 in the table and then find the corresponding z\mathrm{z}-score. If using a calculator or software, we input the area to the left into the inverse CDF function.

STEP 5

After finding the z\mathrm{z}-score using one of the methods in STEP_4, we round the answer to four decimal places as requested.
The z\mathrm{z}-score such that the area to its right under the standard normal distribution is 0.39 is approximately z=0.2743\mathrm{z} = 0.2743.

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