The data suggest the population mean is significantly lower than 38 at \(\alpha = 0.01\), so there is sufficient evidence to conclude that the population mean number of days between haircuts for college students is lower than 38.
\[
\boxed{\text{a. The data suggest the population mean is significantly lower than 38 at } \alpha = 0.01, \text{ so there is sufficient evidence to conclude that the population mean number of days between haircuts for college students is lower than 38.}}
\]