Respuesta :
Answer:
You need to have 538 people in your study.
Step-by-step explanation:
We have that to find our [tex]\alpha[/tex] level, that is the subtraction of 1 by the confidence interval divided by 2. So:
[tex]\alpha = \frac{1 - 0.94}{2} = 0.03[/tex]
Now, we have to find z in the Ztable as such z has a pvalue of [tex]1 - \alpha[/tex].
That is z with a pvalue of [tex]1 - 0.03 = 0.97[/tex], so Z = 1.88.
Now, find the margin of error M as such
[tex]M = z\frac{\sigma}{\sqrt{n}}[/tex]
In which [tex]\sigma[/tex] is the standard deviation of the population and n is the size of the sample.
You practiced on the people at work and found a standard deviation of about 0.37 seconds.
This means that [tex]\sigma = 0.37[/tex]
You want to get a 94% confidence interval that is only 0.06 in width.
This means that [tex]M = \frac{0.06}{2} = 0.03[/tex]
How many people do you need to have in your study?
This is n for which M = 0.03. So
[tex]M = z\frac{\sigma}{\sqrt{n}}[/tex]
[tex]0.03 = 1.88\frac{0.37}{\sqrt{n}}[/tex]
[tex]0.03\sqrt{n} = 1.88*0.37[/tex]
[tex]\sqrt{n} = \frac{1.88*0.37}{0.03}[/tex]
[tex](\sqrt{n})^2 = (\frac{1.88*0.37}{0.03})^2[/tex]
[tex]n = 537.6[/tex]
Rounding up:
You need to have 538 people in your study.
