Small Sample An article includes elapsed times (hours) to lumbar puncture for 19 patients who entered emergency rooms with sudden and severe “thunderclap” headaches (based on data from “Thunderclap Headache and Normal Computed Tomographic Results: Value of Cerebrospinal Fluid Analysis,” by DuPont et al., Mayo Clinic Proceedings, Vol. 83, No. 12). Given that the sample size is less than 30, what requirement must be met in order to treat the sample mean as a value from a normally distributed population? Identify three tools for verifying that requirement.