Answer: p-value is 0.016.
Step-by-step explanation:
Since we have given that
[tex]H_0:\mu=20\\\\H_a:\mu<20[/tex]
Sample mean = 19.4
Sample size n = 50
Standard deviation = 2
We need to find the test statistic value which is given by
[tex]z=\dfrac{\bar{x}-\mu}{\dfrac{\sigma}{\sqrt{n}}}\\\\\\z=\dfrac{19.4-20}{\dfrac{2}{\sqrt{50}}}\\\\\\z=\dfrac{-0.6}{0.28}\\\\z=-2.14[/tex]
p-value is given by
[tex]P(Z>Z_{critical})\\\\=P(Z>-2.14)\\\\=0.016[/tex]
Hence, p-value is 0.016.