Reference no: EM13580766

The design of controls and instruments affects how easily people can use them. A student project investigated this effect by asking 25 right-handed students to turn a knob (with their Page 2right hands) that moved an indicator by screw action. There were two identical instruments, one with right-hand thread (the knob turns clockwise) and the other with a left-hand thread (the knob turns counterclockwise). The table below gives the times in seconds each subject took to move the indicator a fixed distance.

(a) Each of the 25 students used both instruments. Discuss briefly how you would use randomization in arranging the experiment.

(b) The project hoped to show that right-handed people find right-hand threads easier to use. Do an analysis that leads to a conclusion about this issue.

Performance times (seconds) using right-hand and left-hand threads

Subject	Right-thread	Left-thread	Subject	Right-thread	Left-thread
1	113	137	14	107	87
2	105	105	15	118	166
3	130	133	16	103	146
4	101	108	17	1 1 1	123
5	136	115	18	104	135
6	118	170	19	1 1 1	112
7	87	103	20	89	93
8	116	145	21	78	76
9	75	78	22	100	116
10	96	107	23	89	78
11	122	84	24	85	11
12	103	148	25	88	123
13	116	147