Solution:
Given the mean and standard deviation;
[tex]\mu=40,\sigma=8[/tex]The z-score formula is;
[tex]z=\frac{x-\mu}{\frac{\sigma}{\sqrt{n}}}[/tex](a)
[tex]\begin{gathered} x=34,n=1 \\ \\ z=\frac{34-40}{\frac{8}{\sqrt{1}}} \\ \\ z=-0.75 \end{gathered}[/tex](b)
[tex]\begin{gathered} x=34,n=4 \\ \\ z=\frac{34-40}{\frac{8}{\sqrt{4}}} \\ \\ z=-1.5 \end{gathered}[/tex](c)
[tex]\begin{gathered} x=34,n=16 \\ \\ z=\frac{34-40}{\frac{8}{\sqrt{16}}} \\ \\ z=-3 \end{gathered}[/tex]