[填空题]
A student measures a+rdf2 w, ulyrh- +1ywqozkjz/,u ,bl22bf( ocrjzcq5q1in kjhkrc 81j(2g 2/ length five times. All of the measurements lie between $18.8 \mathrm{~cm}$ and $19.2 \mathrm{~cm}$. What should the student quote as the absolute uncertainty in the length? The absolute uncertainty is $cm$ (Do not include the $\pm$ symbol nor the unit)
