Answer:
The sample required is [tex]n = 135[/tex]
Step-by-step explanation:
From the question we are told that
The standard deviation is [tex]\sigma = 9[/tex]
The margin of error is [tex]E = 2[/tex]
Given that the confidence level is 99% then the level of significance is mathematically evaluated as
[tex]\alpha = 100-99[/tex]
[tex]\alpha = 1 \%[/tex]
[tex]\alpha = 0.01[/tex]
Next we will obtain the critical value [tex]\frac{\alpha }{2}[/tex] from the normal distribution table(reference math dot armstrong dot edu) , the value is
[tex]Z_{\frac{\alpha }{2} } = Z_{\frac{0.05 }{2} } = 2.58[/tex]
The sample size is mathematically represented as
[tex]n = [ \frac{Z_{\frac{\alpha }{2} } * \sigma }{E} ]^2[/tex]
substituting values
[tex]n = [ \frac{ 2.58 * 9 }{2} ]^2[/tex]
[tex]n = 135[/tex]
