1. Sources and Examples of internal validity independent variable-cause-dependent variable-effect
2. History- when conducting an experiment, historical events may emerge and bring confusion with the results. In most cases, the anticipated events affects the dependent variable and it becomes hard to different the changes brought by independent variable and historical event (Camphell & Stanley, 256). For example, the Head Start program and Sesame Street were produced at the same period. Though Head Start was created before Sesame Street, they both encompass educational information.  In this case, Sesame Street affects the dependent variable of the Head Start.
3. Testing- An experiment has various process before arriving at the final conclusion. Final experiment results are affected by the process of testing and re-testing and people’s behaviors are influenced in the experiment. In other words, post-test and pretest acts a threat and improves the score (Camphell & Stanley, 257).  For example, when students are tested with examinations on a single subject every week, there is likelihood that they will raise scores through practice. Their ability will increase due to their logical reasoning. 
4. Maturation- this means that in experimental designs, natural process can influence the dependent measure. Maturation can emerge as a result of improvement or because participants can change their behavior when they become bored, hungry and so on (Camphell & Stanley, 257). For example, students who perform best in classroom can decrease their performance in experiment after 45 minutes. This is because either they are more experienced with a particular topic or because the topic is boring.
5. selecting biases- in experimental design, selected subjects are assigned to different groups for final comparison and results. However problems arise when the selected groups are not comparable at the beginning. In instructional experiment, a group may consist of high-ability class but conclusion may be made by an average ability class (Camphell & Stanley, 257).  When there is difference in group prior to the study the overall results will be affected. Selection bias may occur when   individuals chose the group they want to be involved with (self-selection) or when the research selected the group he or she needs in the experiments. For example when the Head Start program was developed, selection bias could occur if the researcher selected children whose parents contacted the program first. Children to these parents could be motivated to learn and finally the student would gain skills not because the program was effective but because the parents were given slots first by the researcher.

 

2 a. According to Babbie, students who act as research participants makes the experiment to lack generalizability. First, it is important to understand that generalizability is applied in experimental setting and   play role in creating findings and conclusions. The point with Babbie is that generalization lack when there are restrictions in the scope of findings (Babbie, 94). Particularly when participants’ observations are derived from small group, it is not possible for the findings to be generalized. Experimental research which involves students lack transparency in that it is hard to analyze the qualitative data and how the participants arrived at the conclusion. Students as participants focus on behaviors and beliefs rather than producing generalized information to the relevant population. In this case, generalizability requires quantitative research in research methodology (Babbie, 98). When talking about generalizability, Babbie means that the study conclusion is derived from a large population based on race, gender and so on. Generalization concepts focus on observation and theory and both are achieved through creating a universal hypothesis. Babbie assert that experimental research which students are the participants lack generalizability because there is lack of validity. The generalizability of a research requires validity and reliability which means that research should have concept measures. In addition, a research should have credibility and conformability so that the drawn findings can make proper inference (Babbie, 130).

 

b.I agree with Babbie’s views that experimental research with college students lack generalizability. Generalization confusion arises on internal and external validity. Internal generalization encompasses conclusion from a group while external generalizability focuses on conclusion made beyond the experimental setting (Babbie, 130). Relating the Bobbie’s views with Cook and Campbell’s, theoretical validity and interpretive of research focus on internal validity or what is known as ‘statistical conclusion validity’ (Camphell & Stanley, 257). College students lack the ability to differentiate between relevant and irrelevant facts and they end up creating invalid results. The point is that there is lack of ethics when students are the participants. They lack ethical consideration and they may feel bored with the experiment and fail to give the correct information. Note that generalization involves taking findings and inferences in a research. In this case, students may have a clue about the research and they may find answers before the experiment so that they can present something similar to the theory (Babbie, 130). In general, college students pose a threat to the research findings due to lack of generalizability. Students are more ambitious and more intelligent and when research uses self-selection in experimental research, students who are socially conscious will volunteer themselves only because they are more extraverted (Babbie, 130).

Reference

Babbie, Earl R. The Basics of Social Research. Belmont, CA: Thomson/Wadsworth, 2008. Print

 Camphell & Stanley “What do you think?”