Question

? = 39 ? = 6 Thus, we have P\left(z < \frac{x - ?}{?}\right) = 0.9 ? P\left(z < \frac{x - 39}{6}\right) = 0.9 ? \frac{x - 39}{6} = 1.28 ? x = 39 + 6 × 1.28 = 46.7 ? 47 minutes Thus, the time that is needed so that 90% of the test takers have time to finish is 47 minutes

          ? = 39
? = 6
Thus, we have
P\left(z < \frac{x - ?}{?}\right) = 0.9
? P\left(z < \frac{x - 39}{6}\right) = 0.9
? \frac{x - 39}{6} = 1.28
? x = 39 + 6 × 1.28
= 46.7
? 47 minutes
Thus, the time that is needed so that 90% of the test takers have time to finish is 47 minutes

? = 39
? = 6
Thus, we have
P(z < (x - ?)/(?)) = 0.9
? P(z < (x - 39)/(6)) = 0.9
? (x - 39)/(6) = 1.28
? x = 39 + 6 × 1.28
= 46.7
? 47 minutes
Thus, the time that is needed so that 90% of the test takers have time to finish is 47 minutes

Added by Brian B.

Elementary Statistics a Step by Step Approach

Allan G. Bluman 9th Edition

Instant Answer

Solved by Expert Narayan Hari

03/07/2022

Step 1

Step 1: The problem states that the mean time to finish the test is 39 minutes (μ = 39) and the standard deviation is 6 minutes (σ = 6). Show more…

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Thanks for your feedback!

μ = 39 σ = 6 Thus, we have μ P(z<*) = 0.9 x σ ⇒P(<*-39) = 0.9 ⇒ 6 x-39 = 1.28 6 ⇒ x = 39 + 6 × 1.28 = 46.7 ≈ 47 minutes Thus, the time that is needed so that 90% of the test takers have time to finish is 47 minutes