Find confidence interval from quadratic fit calibration

Hi all! At this NIST webpage https://www.itl.nist.gov/div898/handbook/pmd/section6/pmd61a.htm from NIST handbook, there's an interesting example on how to apply quadratic fit to load-deflection measurements for calibrating springs. I'm not able to reproduce the same numerical values for the CI, since they are calculated for the predictor variable and not for the response variable. I need the equivalent of

predint

but for x values. Do I have to write a custom function to achieve my goal and obtain the same numerical outputs?

Here's the link with raw data https://www.itl.nist.gov/div898/handbook/pmd/section6/pmd611.htm

Thank you all!!

[Scott MacKenzie]

Quadratic fit? The example shows a linear fit:

[mz123]

Dear Scott,

even if the plot seems linear, if you read the few lines of the post you will see that the equation used too fit the data is quadratic. ;)