The design of controls and instruments affects how easily people can use them. Timothy Sturm investigated this effect in a course project, asking 25 right‑handed students to turn a knob (with their right hands) that moved an indicator by screw action. There were two identical instruments: one with a right‑hand thread (the knob turns clockwise) and the other with a left‑hand thread (the knob turns counterclockwise). The table gives the times, in seconds, each subject took to move the indicator a fixed distance. Performance times (seconds) using right‑hand and left‑hand threads Subject Right Thread Left Thread 1 113 137 2 105 105 3 130 133 4 101 108 5 138 115 6 118 170 7 87 103 8 116 145 9 75 78 10 96 107 11 122 84 12 103 148 13 116 147 Performance times (seconds) using right‑hand and left‑hand threads Subject Right Thread Left Thread 14 107 87 15 118 166 16 103 146 17 111 123 18 104 135 19 111 112 20 89 93 21 78 76 22 100 116 23 89 78 24 85 101 25 88 123 Click to download the data in your preferred format. CSV Excel JMP Mac-Text Minitab14-18 Minitab18+ PC-Text R SPSS TI CrunchIt! Give a 90% confidence interval for the mean time advantage of right‑hand over left‑hand threads. Give your answers to two decimal places.

MATLAB: An Introduction with Applications

6th Edition

ISBN:9781119256830

Author:Amos Gilat

Publisher:Amos Gilat

Chapter1: Starting With Matlab

Section: Chapter Questions

Problem 1P

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

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

Subject	Right Thread	Left Thread
1	113	137
2	105	105
3	130	133
4	101	108
5	138	115
6	118	170
7	87	103
8	116	145
9	75	78
10	96	107
11	122	84
12	103	148
13	116	147

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

Subject	Right Thread	Left Thread
14	107	87
15	118	166
16	103	146
17	111	123
18	104	135
19	111	112
20	89	93
21	78	76
22	100	116
23	89	78
24	85	101
25	88	123

Click to download the data in your preferred format.

CSV Excel JMP Mac-Text Minitab14-18 Minitab18+ PC-Text R SPSS TI CrunchIt!

Give a 90% confidence interval for the mean time advantage of right‑hand over left‑hand threads. Give your answers to two decimal places.

Definition Definition Measure of central tendency that is the average of a given data set. The mean value is evaluated as the quotient of the sum of all observations by the sample size. The mean, in contrast to a median, is affected by extreme values. Very large or very small values can distract the mean from the center of the data. Arithmetic mean: The most common type of mean is the arithmetic mean. It is evaluated using the formula: μ = 1 N ∑ i = 1 N x i Other types of means are the geometric mean, logarithmic mean, and harmonic mean. Geometric mean: The nth root of the product of n observations from a data set is defined as the geometric mean of the set: G = x 1 x 2 ... x n n Logarithmic mean: The difference of the natural logarithms of the two numbers, divided by the difference between the numbers is the logarithmic mean of the two numbers. The logarithmic mean is used particularly in heat transfer and mass transfer. ln x 2 − ln x 1 x 2 − x 1 Harmonic mean: The inverse of the arithmetic mean of the inverses of all the numbers in a data set is the harmonic mean of the data. 1 1 x 1 + 1 x 2 + ...

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