Answer:
97 students must be randomly selected for IQ tests.
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 - 0.95}{2} = 0.025[/tex]
Now, we have to find z in the Z-table as such z has a p-value of [tex]1 - \alpha[/tex].
That is z with a pvalue of [tex]1 - 0.025 = 0.975[/tex], so Z = 1.96.
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.
The Standard Deviation is 15.
This means that [tex]\sigma = 15[/tex]
How many statistics students must be randomly selected for IQ tests if we want 95% confidence that the sample mean is within 3 IQ points of the population mean?
This is n for which M = 3. So
[tex]M = z\frac{\sigma}{\sqrt{n}}[/tex]
[tex]3 = 1.96\frac{15}{\sqrt{n}}[/tex]
[tex]3\sqrt{n} = 1.96*15[/tex]
Simplifying both sides by 3
[tex]\sqrt{n} = 1.96*5[/tex]
[tex](\sqrt{n})^2 = (1.96*5)^2[/tex]
[tex]n = 96.04[/tex]
Rounding up(as with a sample size of 96 the margin of error will be slightly above 3):
97 students must be randomly selected for IQ tests.
