>Instead of treating each as exactly 7 feet, we can instead say that each is somewhere between a minimum of 6.9 feet and a maximum of 7.1. We can write this as

>Instead of treating each as exactly 7 feet, we can instead say that each is somewhere between a minimum of 6.9 feet and a maximum of 7.1. We can write this as an interval (6.9, 7.1). This is not how measurements work in physics. You have to measure at least twice (If you measure only once the sample variance will be infinite due to the bessel correction). Only then you can compute the mean value of your measurements and the standard error. Assuming you made two measurements 6.9 and 7.1 you would write length = 7.0 +/- 0.1 . (see https://www.omnicalculator.com/statistics/standard-error?v=trigger_onResult:1,steps_to_show:1,x1:6.9,x2:7.1 https://www.omnicalculator.com/statistics/standard-error?v=t... )