Export data

I carried out a survey with Qualtrics.
Fortunately, I had the demographics data including the email address of each participant.
Out of the thousand or so personalised emails that have been sent by Qualtrics, 500 or so participants started the survey. About 450 finished it. Now, when I export the data, qualtrics only gives me those who at least started the survey. I don't get back the data of those who did not.
Nevertheless, in order to carry out some statistical tests (Student's t) I need the entirety of the data. Not just those who started the survey. Is there a way to "tell" Qualtrics to "give" me the entirety of the data?
Here's what I do (some of what I indicate might be slightly different as I am translating from the French version of Qualtrics):

1. Login to Qualtrics


2. Click on the proper survey


3. Select Data and analysis


4. Export and import


5. Choose a format (say SPSS)


6. Check the box "Download all the fields"


7. Click on Download

Then I unzip the file but only the 500 or so respondents appear. Those who did not answer, yet their data is somewhere in Qualtrics is not retrieved. How to get that data too?

Thanks in advance for any answer.
p_deli
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