Answer: The value of test statistic is 2.442.
Step-by-step explanation:
Since we have given that
n = 238
Sample mean = 23.2 minutes
Standard deviation = 20.26 minutes
Hypothesis :
[tex]H_0:\mu=20\\H_a:\mu\neq 20[/tex]
So, the test statistic value would be
[tex]z=\dfrac{\bar{x}-\mu}{\dfrac{\sigma}{\sqrt{n}}}\\\\z=\dfrac{23.2-20}{\dfrac{20.26}{\sqrt{236}}}\\\\z=2.442[/tex]
Hence, the value of test statistic is 2.442.