A researcher reports that "Students were randomly assignment to intervention or a control group; the two groups did not differ significantly prior to the start of the intervention. At the end of the study, those receiving the intervention showed statistically significant improvement (p < 0.05) in reading fluency, as compared to those in the control group." Which of the following is NOT a valid inference based on this statement.
A. We can infer that the samples come from two different populations at the end of the study.
B. We can assume that the two groups had identical means and standard deviations at the beginning of the study.
C. The probability that the two groups came from the same population was less than 5%.
D. There is about a 1 in 20 chance that the researcher is incorrectly inferring that the two groups, post-intervention, belong to different populations.
1 answer
Well, you did not give any other choices but if you chose A I suspect you are correct.