91Ó°ÊÓ

The null hypothesis is,

$H_0:\mathrm{μ}=55$years.

The alternative hypothesis is,

$H_0:\mathrm{μ}<55$years.

According to the definition of the type I error it is to reject a null hypothesis when it is true. A type I error would occur in fact $H_0:\mathrm{μ}=55years$true, that is the mean age at diagnosis of all people with early-onset dementia is $55years$old, but the results of the sampling lead to conclude that the mean age at diagnosis of all people with early-onset dementia is less than$55years$old.

According to the definition of the type II error, it is to not reject a null hypothesis when it $\left(H_0\right)$is false. A type II error would occur in fact $\mathrm{μ}=55years$ is not to be rejected, but the results of the sampling fall to lead to conclude that the mean age at diagnosis of all people with early-onset dementia is$55$years old.

A correct decision would occur if the true null hypothesis is not rejected or a false null hypothesis is rejected. Here, in the fact the mean RDA of adult females is and the results of the sampling do not lead to rejection, so is a correct decision; or the mean RDA of adult males is and the results of the sampling lead to that conclusion.