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A random sample of 16 pharmacy customers showed the waiting times below (in minutes).

22 14 25 15 19 15 17 21 15 16 23 16 29 21 22 21

Required:
a. Find a 90 percent confidence interval for μ, assuming that the sample is from a normal population.
b. The 90% confidence interval ______ to ______

Respuesta :

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Answer:

(17.736 ; 21.139)

Step-by-step explanation:

Given the data:

22 14 25 15 19 15 17 21 15 16 23 16 29 21 22 21

Confidence interval ; (C. I) :

Mean ± Zcritical * σ/sqrt(n)

The mean value for the data:

Mean = Σx / n

n = 16

Σx = 311

Mean = 311 / 16 = 19.4375

Zcritical at 90% = 1.645

σ = sqrt[Σ(x - mean)² / n]

Using calculator :

σ = 4.138

19.4375 ± 1.645 * 4.138/sqrt(16)

19.4375 ± 1.645 * 4.138/4

19.4376 ± 1.7017525

Lower bound = 19.4376 - 1.7017525 = 17.736

Upper bound = 19.4376 + 1.7017525 = 21.139

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