Hi all, newbie here who has been out of statistics for a while. I am attempting to test for two questions for an intervention that was conducted that involved the measurement of a test score prior to the intervention, monthly throughout the intervention, and after the intervention:
1. Is the reduction in score between the pre test and post test significant between observation and intervention group?
2. For the group in the intervention, does the length of time that they participated in the intervention lead to a more optimal post test score? I measured test scores monthly for six months throughout the intervention.
I thought that I should use a t test from the difference in means, but I am not feeling confident.
Also, there is bias in my groups in that they were not randomly selected, but rather self selected on whether they wanted to participate. With that in mind, is it even appropriate to measure significance?
Thanks for any help you can offer.
1. Is the reduction in score between the pre test and post test significant between observation and intervention group?
2. For the group in the intervention, does the length of time that they participated in the intervention lead to a more optimal post test score? I measured test scores monthly for six months throughout the intervention.
I thought that I should use a t test from the difference in means, but I am not feeling confident.
Also, there is bias in my groups in that they were not randomly selected, but rather self selected on whether they wanted to participate. With that in mind, is it even appropriate to measure significance?
Thanks for any help you can offer.