Answer:
[tex]H_0:\mu =873\\\\H_a: \mu<873[/tex]
Step-by-step explanation:
Given : In a study investigating a link between walking and improved​ health, researchers reported that adults walked an average of 873 minutes in the past month for the purpose of health or recreation.
Claim : The true average number of minutes in the past month that adults walked for the purpose of health or recreation is lower than 873 minutes.
i.e. [tex]\mu<873[/tex]
We know that the null hypothesis contains equal sign , then the set of hypothesis for the given situation will be :-
[tex]H_0:\mu =873\\\\H_a: \mu<873[/tex]