()是垄断资本家凭借其在社会生产以及流通中的垄断地位而获得的超过平均利润的高额利润

For gathering data about individuals or groups at different developmental levels, researchers can use two related research designs: longitudinal and cross-sectional. A longitudinal study is one that measures a behavior. or a characteristic of an individual over a period of time, perhaps decades. An example of such a study is the Berkeley Growth Study begun in 1928 by Nancy Bayley. The study focused on a group of 74 white, middle-class newborns. As they grew older, extensive measures of their intellectual, personality, and motor development were recorded. The subjects were studied for more than thirty years. The longitudinal research design is a powerful technique for seeking understandings of the effects of early experiences on later development. Also, differences in stability of behaviors or characteristics at different ages can be determined. Longitudinal studies, however, are expensive to conduct, time-consuming, and heavily contingent on the patience and persistence of the researchers. The findings of a longitudinal study may be jeopardized by relocation of subjects to another part of the country and by boredom or irritation at repeated testing. Another disadvantage is that society changes from one time to another and the subjects participating in the study reflect to some degree such changes. The methods of study or the questions guiding the researchers may also change from one time to another. If properly conducted, however, longitudinal studies can produce useful, direct information about development. A cross-sectional study is one in which subjects of differing ages are selected and compared on a specific behavior. or characteristic. They are alike with respect to socioeconomic status, sex, or educational level. For example, a researcher may be interested in looking at changes in intelligence over a thirty-year period. Three groups of subjects—ages ten, twenty and thirty, may be selected and tested. Conclusions are drawn from the test data. The cross-sectional research design has the clear advantage of being less expensive to conduct and certainly less time-consuming. The major disadvantage is that different individuals who make up the study sample have not been observed over time. No information about past influences on development or about age-related changes is secured. Like longitudinal studies, the cross-sectional methods cannot erase the generational influence that exists when subjects studied are born at different time. Psychologists are now beginning to use an approach that combines longitudinal and cross-sectional research methods.Which of the following is NOT one of the disadvantages of a longitudinal research?A．The subjects may become irritated at repeated testing.B．The participants in the study may not stay in one place for many years.C．The behavior. of a subject in the study may be measured continuously for many years.D．Social changes may be reflected in the behaviors of the subjects participating in the study.此题为多项选择题。 点击查看答案

我国寓言文学兴盛的黄金时代是()。

A.先秦时期
B.两汉时期
C.魏晋南北朝时期
D.唐宋时期

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