Answered

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14. A cellular telephone company recently conducted research into the length of calls (in
minutes) made by customers. In a random sample of 30 calls, the sample mean was
x= 18.6 minutes and the standard deviation was s=5.2 minutes. Construct and interpret
a 90% confidence interval for true mean call length. (4-step process)

Sagot :

Cricetus

Answer:

The correct answer is "16.987, 20213".

Step-by-step explanation:

Given that,

[tex]n=30[/tex]

[tex]\bar x=18.6[/tex]

[tex]s = 5.2[/tex]

[tex]df=30-1[/tex]

   [tex]=29[/tex]

[tex]\alpha = 0.10[/tex]

By using the table, the critical values of t will be:

= [tex]\pm 1.699[/tex]

Now,

The confidence interval will be:

= [tex]\bar x \pm \frac{t\times s}{\sqrt{n} }[/tex]

By putting the values, we get

= [tex]18.6 \pm \frac{1.699\times 5.2}{\sqrt{30} }[/tex]

= [tex]16.987,20.213[/tex]

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