来自chatgpt Sure, here's an example of a time-fixed exposure study design: Suppose researchers want to investigate the effects of a new medication on blood pressure. They recruit 100 participants with high blood pressure and randomly assign them to either the intervention group or the control group. The intervention group is instructed to take the new medication daily for 12 weeks, while the control group is given a placebo pill to take daily for the same 12-week period. Both groups are monitored for any changes in blood pressure over the course of the 12 weeks. At the end of the study, the researchers compare the change in blood pressure between the intervention and control groups. If the medication is effective, they would expect to see a greater decrease in blood pressure in the intervention group compared to the control group. In this example, the exposure (the medication) is given for a fixed amount of time (12 weeks), and both groups are followed for the same period of time, allowing for a comparison of the effects of the exposure on the outcome of interest (blood pressure). This is an example of a time-fixed exposure study design.
In an exposure-fixed study design, the exposure is fixed or constant across all participants, while the length of follow-up may vary. On the other hand, in a time-fixed study design, the length of exposure is fixed for all participants, while the intensity or dose of exposure may vary. An example of a time-fixed study design would be a study investigating the effects of long-term exposure to air pollution on lung function. In this type of study, participants may be followed for a fixed period of time (e.g., 5 years) and their exposure to air pollution is measured over that time period. The intensity or dose of exposure may vary depending on a variety of factors (e.g., location of residence, occupation), but the length of follow-up is fixed. To differentiate between the two study designs, it is important to consider whether the exposure or the length of follow-up is fixed or constant across participants. In an exposure-fixed study design, the exposure is constant across participants, while in a time-fixed study design, the length of follow-up is constant across participants.
Chatgpt帮你提供了一些reference Sure! Here are some references on exposure-fixed study designs: Taylor, J. M., & Fahey, M. T. (2018). Design considerations for exposure-fixed, non-randomised toxicity and carcinogenicity studies. Regulatory Toxicology and Pharmacology, 94, 113-122. https://doi.org/10.1016/j.yrtph.2018.02.017 Rothman, K. J., Greenland, S., & Lash, T. L. (2012). Modern epidemiology (3rd ed.). Lippincott Williams & Wilkins. Hernán, M. A., & Robins, J. M. (2018). Causal inference. Chapman and Hall/CRC. These references discuss various aspects of exposure-fixed study designs, including their design considerations, applications in toxicology and carcinogenicity studies, and their use in causal inference. Certainly! Here are some references on time-fixed study designs: Hulley, S. B., Cummings, S. R., Browner, W. S., Grady, D. G., & Newman, T. B. (2013). Designing clinical research (4th ed.). Wolters Kluwer/Lippincott Williams & Wilkins. Glynn, R. J., Rosner, B., & Koenen, K. C. (2019). Investigating the longitudinal association between traumatic events and depression in the Nurses' Health Study II. Annals of Epidemiology, 30, 10-15. https://doi.org/10.1016/j.annepidem.2018.11.005 Little, R. J. A., & Rubin, D. B. (2019). Statistical analysis with missing data (3rd ed.). John Wiley & Sons. These references discuss various aspects of time-fixed study designs, including their design considerations, applications in clinical research and epidemiology, and statistical methods for analyzing data from these designs.
书或者网上的例子，都欢迎。 谢谢！
Sure, here's an example of a time-fixed exposure study design: Suppose researchers want to investigate the effects of a new medication on blood pressure. They recruit 100 participants with high blood pressure and randomly assign them to either the intervention group or the control group. The intervention group is instructed to take the new medication daily for 12 weeks, while the control group is given a placebo pill to take daily for the same 12-week period. Both groups are monitored for any changes in blood pressure over the course of the 12 weeks. At the end of the study, the researchers compare the change in blood pressure between the intervention and control groups. If the medication is effective, they would expect to see a greater decrease in blood pressure in the intervention group compared to the control group. In this example, the exposure (the medication) is given for a fixed amount of time (12 weeks), and both groups are followed for the same period of time, allowing for a comparison of the effects of the exposure on the outcome of interest (blood pressure). This is an example of a time-fixed exposure study design.
My god. I googled for a month but found nothing. your chatgpt gives a clear answer.
请问你的这个例子，是exposure-fixed，还是time-fixed？ 如何区分这两者？
哈哈，CHATGPT是不是特棒！ 你可以试下，非常非常impressive
On the other hand, in a time-fixed study design, the length of exposure is fixed for all participants, while the intensity or dose of exposure may vary. An example of a time-fixed study design would be a study investigating the effects of long-term exposure to air pollution on lung function. In this type of study, participants may be followed for a fixed period of time (e.g., 5 years) and their exposure to air pollution is measured over that time period. The intensity or dose of exposure may vary depending on a variety of factors (e.g., location of residence, occupation), but the length of follow-up is fixed.
To differentiate between the two study designs, it is important to consider whether the exposure or the length of follow-up is fixed or constant across participants. In an exposure-fixed study design, the exposure is constant across participants, while in a time-fixed study design, the length of follow-up is constant across participants.
Sure! Here are some references on exposure-fixed study designs: Taylor, J. M., & Fahey, M. T. (2018). Design considerations for exposure-fixed, non-randomised toxicity and carcinogenicity studies. Regulatory Toxicology and Pharmacology, 94, 113-122. https://doi.org/10.1016/j.yrtph.2018.02.017 Rothman, K. J., Greenland, S., & Lash, T. L. (2012). Modern epidemiology (3rd ed.). Lippincott Williams & Wilkins. Hernán, M. A., & Robins, J. M. (2018). Causal inference. Chapman and Hall/CRC. These references discuss various aspects of exposure-fixed study designs, including their design considerations, applications in toxicology and carcinogenicity studies, and their use in causal inference.
Certainly! Here are some references on time-fixed study designs: Hulley, S. B., Cummings, S. R., Browner, W. S., Grady, D. G., & Newman, T. B. (2013). Designing clinical research (4th ed.). Wolters Kluwer/Lippincott Williams & Wilkins. Glynn, R. J., Rosner, B., & Koenen, K. C. (2019). Investigating the longitudinal association between traumatic events and depression in the Nurses' Health Study II. Annals of Epidemiology, 30, 10-15. https://doi.org/10.1016/j.annepidem.2018.11.005 Little, R. J. A., & Rubin, D. B. (2019). Statistical analysis with missing data (3rd ed.). John Wiley & Sons. These references discuss various aspects of time-fixed study designs, including their design considerations, applications in clinical research and epidemiology, and statistical methods for analyzing data from these designs.