In: Statistics and Probability
An article reported the following data on oxidation-induction time (min) for various commercial oils: 88 104 130 160 180 195 132 145 213 105 145 151 153 136 87 99 95 119 129 (a) Calculate the sample variance and standard deviation. (Round your answers to three decimal places.) s2 = min2 s = min (b) If the observations were reexpressed in hours, what would be the resulting values of the sample variance and sample standard deviation? Answer without actually performing the reexpression. (Round your answer to three decimal places.) s2 = hr2 s = hr
Sol:
X | X - mean | (X-mean)2 | X2 |
88 | -47.0526 | 2213.95014 | 7744 |
104 | -31.0526 | 964.265928 | 10816 |
130 | -5.05263 | 25.5290859 | 16900 |
160 | 24.94737 | 622.371191 | 25600 |
180 | 44.94737 | 2020.26593 | 32400 |
195 | 59.94737 | 3593.68698 | 38025 |
132 | -3.05263 | 9.31855956 | 17424 |
145 | 9.947368 | 98.9501385 | 21025 |
213 | 77.94737 | 6075.79224 | 45369 |
105 | -30.0526 | 903.160665 | 11025 |
145 | 9.947368 | 98.9501385 | 21025 |
151 | 15.94737 | 254.31856 | 22801 |
153 | 17.94737 | 322.108033 | 23409 |
136 | 0.947368 | 0.89750693 | 18496 |
87 | -48.0526 | 2309.0554 | 7569 |
99 | -36.0526 | 1299.79224 | 9801 |
95 | -40.0526 | 1604.2133 | 9025 |
119 | -16.0526 | 257.686981 | 14161 |
129 | -6.05263 | 36.634349 | 16641 |
2566 | -2.8E-14 | 22710.9474 | 369256 |
s^2=sample variance=22710.9474/19-1=1261.719 min^2
s=sample standard deviation=sqrt(1261.719)=35.521 min
Solutionb:
1 hour=60 min
1min=1/60 hr
s^2=sample variance=22710.9474/19-1=1261.719 min^2=1261.719 (1/60 )^2hr^2=0.3504775=0.350 hour^2
s=sample standard deviation=sqrt(1261.719)=35.521 min=35.521/60=0.5920167 hour=0.592 hour