In: Statistics and Probability
A Company manufactures an insulation stripping tool that peels
insulation from electric wiring 1/8” to 1/4” in diameter. A sample
of sixteen tools were randomly selected from the warehouse in order
to test the pull-force (in pounds) of the product. The pull-forces
of the sixteen tools are shown below:
12.6 12.9 13.4 12.3 13.6 13.5 12.6 13.1 12.5 13.2 13.0 12.5 13.5
12.4 12.2 12.7
Determine: Mean, Median, Qaurtile1, Qaurtile3, Range, S.E.M., Mode,
Outlier(s), Variance, Standard Deviation,
Inter-Quartile Range, Max & Min. Note: All calculations must be
shown.
(1)
Mean = 206/16 = 12.875
(2)
Arranging data in ascending order, we get
12.2, 12.3, 12.4, 12.5, 12.5, 12.6, 12.6, 12.7, 12.9, 13.0, 13.1, 13.2, 13.4, 13.5, 13.5, 13.6
n = 16
Median = (16 + 1)/2 th item = average of 8th & 9th items= (12.7 + 12.9)/2 = 12.8
So,
Median = 12.8
(3)
Bottom half is:
12.2, 12.3, 12.4, 12.5, 12.5, 12.6, 12.6, 12.7
The middle of these numbers = 12.5
So,
Quartile1 = Q1 = 12.5
(4)
Upper half is:
12.9, 13.0, 13.1, 13.2, 13.4, 13.5, 13.5, 13.6
Middle of these numbers = 13.3
So,
Quartile 3 = Q3 = 13.3
(5)
Range = Maximum - Minimum = 13.6 - 12.2 = 1.4
(6)
S.E.M.= Standard Error of Mean = Standard Deviation/
= 0.4640/ = 0.116
(7)
Mode = 12.5, 12.6, 13.5
since these 3 values occur 3 times
(8)
IQR = Q3- Q1 = 13.3 - 12.5 = 0.8
Lower = Q1 - 1.5 IQR = 12.5 - (1.5 X 0.8) = 12.5 - 1.2 = 11.3
Upper = Q3 + 1.5 IQR = 13.3 + (1.5 X 0.8) = 13.3 + 1.2 = 14.5
Since all values are within these limits, there are no outliers.
(9)
x | (x- | (x - )2 |
12.6 | - 0.275 | 0.0756 |
12.9 | 0.025 | 0.0001 |
13.4 | 0.525 | 0.2756 |
12.3 | - 0.575 | 0.3306 |
13.6 | 0.725 | 0.5256 |
13.5 | 0.625 | 0.3906 |
12.6 | - 0.275 | 0.0756 |
13.1 | 0.225 | 0.0506 |
12.5 | - 0.375 | 0.1406 |
13.2 | 0.325 | 0.1056 |
13.0 | 0.125 | 0.0156 |
12.5 | - 0.375 | 0.1406 |
13.5 | 0.625 | 0.3906 |
12.4 | - 0.475 | 0.2256 |
12.2 | - 0.675 | 0.4556 |
12.7 | - 0.175 | 0.0306 |
Total = | 3.23 |
Variance = 3.23/15= 0.2153
(10)
Standard deviation =
(11)
Inter-Quartile Range = IQR = Q3- Q1 = 13.3 - 12.5 = 0.8
(12)
Max= 13.6
Min = 12.2