Answer: 306
Step-by-step explanation:
Formula to find sample size:
[tex]n=(\dfrac{\sigma\times z^*}{E})^2[/tex] , where [tex]\sigma[/tex] = standard deviation, E = margin of error, z* = critrical z-value.
As per given,
[tex]\sigma=9.5 , E=1.4[/tex]
Critical z-value for 99% confidence = 2.576
Now , the minimum sampl size :[tex]n=(\dfrac{9.5\times2.576}{1.4})^2[/tex]
[tex]\Rightarrow\ n=305.5504\approx306[/tex]
Hence, the required sample size = 306
