reasonable estimate of the target group is not made, there is no point in extending relevant estimates to groups outside the target group. Internal validity Internal validity refers to the degree to which knowledge inferences based on empirical research approximate the actual attitudes or behavioural patterns of the target population. Constructive validity Construct validity involves the generality of empirical inferences and aims to evaluate whether a research design is a reasonable and targeted assessment of the target theory. Causal validity Causal validity is similar to the "identification problem" in economics, which examines whether an empirical design can effectively eliminate interference factors and provide accurate evidence for determining causal effects or mechanisms. Statistical validity Statistical validity refers to whether there is a significant and stable statistical relationship between the core causal factors of the study at the empirical level. The most common test of statistical validity is repeated testing of the same sample of the target population. External validity External validity refers to how empirical inferences apply to populations other than the target population. Experimental designs Laboratory experiment Laboratory experiments place subjects in specific environments and examine how individuals make specific political decisions (such as voting, jury trials, and legislation). Laboratory experiments have stricter control over the experimental site and time, and the entire experimental process must be completed under the supervision and guidance of the researcher. Questionnaires are usually used to collect the subjects' personal information and experimental results. Laboratory experiments are usually carried out in independent laboratories, reflecting the researcher's understanding and attitude towards the information contained in time and space. Laboratory experiments emphasize the control environment and other non-experimental elements to maximize the exclusion of interference factors and accurately measure the causal effects of researched factors. The laboratory itself does not refer to the specialized laboratory used in the natural sciences. Classrooms, activity rooms, or other independent spaces can be used as experimental places. Conjoint survey The conjoint survey experiment is a method for examining multidimensional preferences. Lab-in-the-field experiment At one extreme, "pure" laboratory experiments are carried out in environments that researchers highly control. Students are often a convenient sample in lab experiments because they are easy to participate in and able to follow the experimental instructions reliably. Natural experiments are the kind of design at another extreme. In natural experiments, participants are in the daily-live conditions, and they do not know they are being observed. Lab-in-the-field experimental