Errors are normally classified into two broad categories: systematic errors and random errors. Systematic errors: Systematic errors are due to identified causes and can, in principle, be eliminated. Errors of this type result in measured values that are consistently too high or consistently too low. Systematic error can arise from innumerable sources, including factors involved in the choice or recruitment of a study population and factors involved in the definition and measurement of study variables. The inverse of bias is validity, also a desirable attribute. Random Errors: Random errors are caused by sources that are not immediately obvious and it may take a long time trying to figure out the source. Random error is also called a statistical error because it can be gotten rid of in measurement by statistical means because it is random in nature. Random error can be caused by numerous things, such as inconsistencies or imprecision in equipment used to measure data, in experimenter measurements, in individual differences between participants who are being measured, or in experimental procedures. Key Points Curriculum: In education, a curriculum is broadly defined as the totality of student experiences that occur in the educational process. The term often refers specifically to a planned sequence of instruction, or to a view of the student's experiences in terms of the educator's or school's instructional goals. A curriculum is the combination of instructional practices, learning experiences, and students' performance assessments that are designed to bring out and evaluate the target learning outcomes of a particular course. Attrition: The process of reducing something’s strength or effectiveness through sustained attack or pressure. Content choice bias: Giving priority to particular content over others in the curriculum by curriculum designer. Subject effects: In scientific research, the subject-expectancy effect, is a form of reactivity that occurs when a research subject expects a given result and therefore unconsciously affects the outcome, or reports the expected result. Conclusion: since content choice bias is correlated to the curriculum which affects the pedagogy of the curriculum. Hence, option (2) is correct.