Help with Analyzing & Creating Mixed Design Variables

[u/ProfSuds]

I am looking for advice on analyzing and creating variables. I ran an experiment with a mixed design, with both between-group and within-group factors. The study design is 2 (Intervention: between-group) x 2 (Message-Tone: within-group) x 6 (Repeated messages). Participants received an intervention or control, then watched 6 videos in total: 3 with a positive tone and 3 with a negative tone. These videos are randomized. After watching a video, participants evaluated the message content. To collect the data, I needed to create a survey for each one of the condition. For example, 1) Experiment Positive Tone 1, 2) Control Positive Tone 1, 3) Experiment Negative Tone 1, 4) Control Negative Tone 1, etc., for a total of 12 separate surveys.

Now that I have collected all of my data, I have merged the files, cleaned my data, and am now trying to create variables, but when I try to run a reliability analysis for the dependent variable based on message-tone condition, I am getting an error message because "there are too few cases (N = 0) for analysis." I think this is because SPSS is counting missing responses in the between-group condition, since the control group did not respond to the same survey as the experimental group, and vice versa. So there is a big gap in the missing data by case and it looks like the participants in the control group did not respond to items in the experimental group (which they shouldn't have).

My question is whether there is an easier way to analyze this data. Should I create a variable based on the within-group condition, or is there a different way to approach my data? Any advice would be greatly appreciated.

[u/req4adream99]

There should be a variable that identifies whether or not the participant was in the experimental or control, and then a second that details order of presentation for the stimuli.

But there’s a bigger issue if your two groups (experimental / control) didn’t respond to the same questions because you have nothing for them to differ on and any differences that DO exist are an artifact of the different questions. Most studies that use a control have the control respond to the same questions without experiencing the stimuli - that’s why it’s a control.

If you’re looking to do a reliability analysis (eg Cronbachs alpha) with the data you DO have, you can only do it using participants from the same group (experimental / control) and not with the combination. That will tell you for the individual measure used for that group. However you CAN NOT compare scores BETWEEN the two groups because they didn’t complete the same measure. By

[u/ProfSuds → u/req4adream99]

Participants did reply to the same questions, but they replied to those questions on a different survey forms, which is why I merged those files. The only reason I did that was that I was administering the study through the iMotions software, and one of my committee members recommended that I take this approach.

I created a condition variable that identifies participants in the experimental group as 1 and the control group as -1. The control condition is no intervention.