Thiết kế câu hỏi, nên tránh câu hỏi giả định và các câu hỏi về tham khảo và so sánh.

Nghiên cứu thử nghiệm (experimental study) khác biệt so với nghiên cứu tương quan (correlational study) ở khả năng thiết lập mối quan hệ nhân quả. Trong nghiên cứu thử nghiệm, nhà nghiên cứu chủ động thao tác một hoặc nhiều biến độc lập và đo lường tác động của chúng lên biến phụ thuộc, đồng thời kiểm soát các biến ngoại lai. Điều này cho phép kết luận về nguyên nhân và hệ quả. Nghiên cứu tương quan chỉ tìm hiểu mối liên hệ giữa các biến mà không chứng minh được biến nào gây ra biến nào. Do đó, đáp án đúng là nghiên cứu thử nghiệm có thể chứng minh được các liên hệ nguyên nhân và hệ quả rõ ràng hơn.

Nghiên cứu theo dõi là một loại nghiên cứu trong đó các đối tượng được theo dõi trong một khoảng thời gian dài để theo dõi sự thay đổi của họ theo thời gian.

Nghiên cứu thuần tập (cohort study) theo dõi một nhóm người theo thời gian để xem xét sự phát triển của bệnh hoặc kết quả. Trong nghiên cứu thuần tập, đối tượng được chọn dựa trên việc họ có tiếp xúc với một yếu tố nguy cơ hay không, chứ không phải dựa trên việc họ đã mắc bệnh hay chưa. Do đó, sai số chọn thường thấp hơn so với các nghiên cứu quan sát khác như nghiên cứu bệnh chứng (case-control study), nơi đối tượng được chọn dựa trên tình trạng bệnh, làm tăng khả năng sai số chọn do cách chọn nhóm chứng.

Giá trị suy luận căn nguyên (khả năng chứng minh mối quan hệ nhân quả) của các thiết kế nghiên cứu được sắp xếp như sau:

* Nghiên cứu bệnh chứng (c): Đây là thiết kế yếu nhất trong việc suy luận căn nguyên vì nó bắt đầu với bệnh và hồi cứu để tìm yếu tố nguy cơ. Điều này dễ dẫn đến sai lệch do nhớ lại và khó xác định trình tự thời gian.
* Nghiên cứu thuần tập hồi cứu (b): Nghiên cứu này mạnh hơn bệnh chứng vì nó xác định кого кого кого кого кого кого кого кого кого кого кого кого кого кого кого кого кого кого кого кого кого кого кого кого кого кого кого кого кого кого кого кого кого кого кого кого кого кого кого кого кого кого кого кого кого кого кого кого кого кого кого кого кого кого кого кого кого кого кого кого кого кого кого кого кого кого кого кого кого кого кого кого кого кого кого кого кого кого кого кого кого кого кого кого кого кого кого кого кого кого кого кого кого кого кого кого кого кого кого кого кого кого кого кого кого кого кого кого кого кого кого кого кого кого кого кого кого кого кого кого кого кого кого кого кого кого кого кого кого кого кого кого кого кого кого кого кого кого кого кого кого кого кого кого кого кого кого кого кого кого кого кого кого кого кого кого кого кого кого кого кого кого кого кого кого кого кого кого кого кого кого кого кого кого кого кого кого кого кого кого кого кого кого 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Phương pháp nghiên cứu bệnh chứng là một phương pháp nghiên cứu hồi cứu (retrospective), trong đó người ta so sánh một nhóm người mắc bệnh (nhóm bệnh) với một nhóm người không mắc bệnh (nhóm chứng) để tìm hiểu xem có những yếu tố nào trong quá khứ có thể liên quan đến sự phát triển của bệnh. Một trong những nhược điểm lớn nhất của phương pháp này là sự phụ thuộc vào hồ sơ và trí nhớ của đối tượng nghiên cứu, điều này có thể dẫn đến sai lệch (bias) do thông tin không đầy đủ hoặc không chính xác. Vì hồ sơ bệnh án có thể không đầy đủ hoặc bị mất, và người tham gia có thể không nhớ chính xác các sự kiện hoặc yếu tố phơi nhiễm trong quá khứ. Do đó, đáp án "Tài liệu, hồ sơ cần thiết không hòan chỉnh" là nhược điểm lớn nhất của phương pháp này. Các đáp án khác có thể đúng trong một số trường hợp nhất định, nhưng không phải là nhược điểm cốt lõi của phương pháp nghiên cứu bệnh chứng như việc thiếu tài liệu hoặc hồ sơ hoàn chỉnh.