Trendline does not match data

Question

Like the title says, I have a scatter plot with trendline indicating a slope value of -19.72:

But that same data provided to SLOPE yields a value of -13.8646:

And likewise for the LINEST formula; slope value is -13.8646:

What gives? Why is the trendline formula so wrong? Yes, I'm aware of the whole treachery of the trendline legend numeric precision dictating calculation precision and it obviously does not apply here.

Before someone slides in complaining about that R-value, here is the exact same issue with a different plot that has an R^2 near 1:

Original file download here

Answer 1

Thanks for the reply. As you can see, something is pretty clearly not working as intended. Having already done the initial legwork of noticing, documenting, researching, solution-testing, and, finally, reporting the issue (as well as uploading a source file to a third party for troubleshooters to investigate since these forums lack such a feature)..... I don't see any compelling reason to post my question into a different community.

If Microsoft had a quality control department (do they?), well, they now have everything available to investigate on their own and come up with a solution on their own.

For anyone else experiencing this problem, I would recommend just don't even bother with the charts.

Answer 2

Hi ,  Thank you for posting in the Microsoft Community.

Based on your message, it sounds like you're experiencing issues with your Excel. For this question is already out of my specialty and this is more complex which requires assistance upfront. I suggest posting your case here on: Welcome to the Excel Community - Microsoft Community Hub. Our experts can help you with your concerns. This community have a wealth of resources when it comes to this concerns.

We will also leave the thread open for all volunteer moderators to join us and share their opinions/suggestions to help you address your concerns.

Regards,  Nael B.Microsoft Moderator