That is because your sessions are only compared within the same presentation type and audience type. Recall that when you set up a session, you need to select the two types. In result, there are four combinations:
- Informative presentation to General audience
- Informative presentation to Technical audience
- Persuasive presentation to General audience
- Persuasive presentation to Technical audience
If your score of the informative presentation to general audience is compared to persuasive presentation to technical audience, then the comparison isn't very meaningful because the scoring requirements are different. For example, a good persuasive presentation is more emotional than an informative presentation thus would require higher vocal variability (Pitch variability, volume variability, etc.) to express the emotion involved.
When you compare the scores on Dashboard page, select the Presentation Type and Audience Type at the bottom of the screen and click "Submit" before you start comparing. The results will show you all the recent presentations within the same category. Now you are comparing apples to apples and pears to pears.