Dana and Dan are both conducting a study to examine the relationship between number of pregnancies and level of cognitive decline in women over the age of 60. Dana randomly selects a sample of 50 women over the age of 60 who are patients of a large neurology clinic and then administers the Mini-Cog to assess their level of cognitive impairment. She also records the number of pregnancies for each woman. Dan, on the other hand, randomly selects the health records for 50 women over the age of 60 who have been patients of the large neurology clinic within the past 10 years. The health records contain information about the women's cognitive impairment level and number of pregnancies. Who has the better approach for obtaining the sample? Explain.