Answer:
Null hypothesis: [tex]H_0:\; \mu = 48\; ^\circ\rm F[/tex].
Alternative hypothesis: [tex]H_1:\; \mu \ne 48\; \rm ^\circ F[/tex].
Step-by-step explanation:
In hypothesis testing, the alternative hypothesis [tex]H_1[/tex] represents the claim that is being tested. According to the claim in this question, the true (population) mean [tex]\mu[/tex] is "incorrect," or not equal to ("[tex]\ne[/tex]") the proposed value of [tex]48\; \rm ^\circ F[/tex]. Hence, the alternative hypothesis for this question would be [tex]H_0:\; \mu \ne 48\; \rm ^\circ F[/tex].
On the other hand, the null hypothesis represents what happens when that claim is disproved; it should always use the equal sign ("[tex]=[/tex]".) In this question, that's the same as saying that the (population) mean [tex]\mu[/tex] is indeed equal to [tex]48\; \rm ^\circ F[/tex]. Hence, the null hypothesis for this question would be: [tex]H_1:\; \mu = 48\; \rm ^\circ F[/tex].