A factory manufactures nuts and bolts of various sizes. The measurement of inner diameters of 1000 nuts gave the following frequency table:
Diameter (mm) | 43-45 | 46-48 | 49-51 | 52-54 | 55-57 |
No. of Nuts | 175 | 236 | 200 | 196 | 193 |
Determine the mean inner diameter per nut.
48
50
52
54
As we have learnt @3143
The given table is in inclusive form of frequency distribution. We first convert it into an
exclusive form and write it in the form
Diameter (in mm) | 42.5-45.5 | 45.5-48.5 | 48.5-51.5 | 51.5-54.5 | 54.5-57.5 |
No. of Nuts | 175 | 236 | 200 | 196 | 193 |
the width of the class intervel is h = 3
Let the Shift (Assumed mean) be a = 50
Diameter (mm) | ||||
42.5-45.5 45.5-48.5 48.5-51.5 51.5-54.5 54.5-57.5
|
44 47 50 53 56
|
175 236 200 196 193 |
-2 -1 0 1 2
|
-350 -236 0 196 286 |
Thus the mean inner diameter is
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