A student measures the width of an object several times and records the following data: 2.3 cm, 2.4 cm, 2.2 cm, 2.3 cm, 2.3 cm, 2.2 cm, and 2.8 cm. He decides to represent his data the following way:
2.3 + 2.4 + 2.2 + 2.3 + 2.3 + 2.2 + 2.8 = 16.5
16.5 ÷ 7 = 2.357 cm
(2.8 – 2.2) ÷ 2 = 0.3 cm
Therefore, the average value is 2.4 ± 0.3 cm. A teacher tells the student that his report should read 2.3 ± 0.1 cm.
How did the teacher get this result and what type of error did the student commit?

Abox that has self-contained cable clamps holds two light switches. a two-wire no. 12 cable with ground feeds the box, and a pair of two-wire no. 12 cables (four conductors) with ground wires leaves the box to feed the light fixtures. the second switch is fed by a no. 12 jumper wire from the first switch. which one of the following box combinations would furnish the minimum allowable volume? a. two 3-inch × 2-inch × 21⁄2-inch gangable device boxes b. two 3-inch × 2-inch × 11⁄2-inch gangable device boxes c. two 3-inch × 2-inch × 23⁄4-inch gangable device boxes d. two 3-inch × 2-inch × 21⁄4-inch gangable device boxes