Study the Following Research Plan and Identify Any Variables And/or

Study the following research plan and identify any variables and/or conditions that may pose a threat to the internal validity of the experiment. Name the most likely threats to internal validity, and explain each briefly in terms of the research plan.Research plan: The researcher wants to determine the effect of a special reading program on the reading achievement of inner-city children. The study will be longitudinal, extending from the beginning of grade 2 to the end of grade 3. He identifies 50 children who are nonreaders at the end of grade 1; these children will receive the special program. He randomly selects 50 other children in the same school and grade level to serve as a control group. The researcher administers the same reading test to both groups at the start of grade 2 and at the end of grade 3. By the end of grade 3, there are 27 children who have remained in the special program and 36 children in the control group. The researcher compares the reading gains of the two groups and finds that each group has gained an average of 1.6 years in reading grade placement.