Answer:
The correct option is d
Step-by-step explanation:
From the question we are told that
The sample size is n = 64
The mean is [tex]\= x = 320[/tex]
The standard deviation is [tex]\sigma = 120[/tex]
Generally the standard error of the mean is mathematically represented as
[tex]\sigma_x = \frac{\sigma}{ \sqrt{n} }[/tex]
=> [tex]\sigma_x = \frac{120}{ \sqrt{64} }[/tex]
=> [tex]\sigma_x =15[/tex]
