In: Math
Eyeglassomatic manufactures eyeglasses for different retailers. They test to see how many defective lenses they made the time period of January 1 to March 31. Table #11.2.4 gives the defect and the number of defects.
Table #11.2.4: Number of Defective Lenses
|
Defect type |
Number of defects |
|
Scratch |
5865 |
|
Right shaped - small |
4613 |
|
Flaked |
1992 |
|
Wrong axis |
1838 |
|
Chamfer wrong |
1596 |
|
Crazing, cracks |
1546 |
|
Wrong shape |
1485 |
|
Wrong PD |
1398 |
|
Spots and bubbles |
1371 |
|
Wrong height |
1130 |
|
Right shape - big |
1105 |
|
Lost in lab |
976 |
|
Spots/bubble - interim |
976 |
Do the data support the notion that each defect type occurs in the same proportion? Test at the 10% level.
null hypothesis: Ho: each defect type occurs in the same proportion
alternate hypotheiss: Ha:at least one type of defect occur in different proportion
degree of freedom =categories-1 =13-1=12
for 12 df and 0.1 level ; rejection region
>18.549
applying chi square goodness of fit test:
| observed | Expected | Chi square | |||
| category | Probability(p) | Oi | Ei=total*p | R2i=(Oi-Ei)2/Ei | |
| Scratch | 1/13 | 5865.000 | 1991.615 | 7533.135 | |
| Right shaped - small | 1/13 | 4613.000 | 1991.615 | 3450.293 | |
| Flaked | 1/13 | 1992.000 | 1991.615 | 0.000 | |
| Wrong axis | 1/13 | 1838.000 | 1991.615 | 11.849 | |
| Chamfer wrong | 1/13 | 1596.000 | 1991.615 | 78.585 | |
| Crazing, cracks | 1/13 | 1546.000 | 1991.615 | 99.705 | |
| Wrong shape | 1/13 | 1485.000 | 1991.615 | 128.870 | |
| Wrong PD | 1/13 | 1398.000 | 1991.615 | 176.931 | |
| Spots and bubbles | 1/13 | 1371.000 | 1991.615 | 193.392 | |
| Wrong height | 1/13 | 1130.000 | 1991.615 | 372.753 | |
| Right shape - big | 1/13 | 1105.000 | 1991.615 | 394.698 | |
| Lost in lab | 1/13 | 976.000 | 1991.615 | 517.909 | |
| Spots/bubble - interim | 1/13 | 976.000 | 1991.615 | 517.909 | |
| total | 1.000 | 25891 | 25891 | 13476.029 |
as test statitic 13476.029 is in critical region; we reject null hypothesis.
we have sufficient evidence at 0.1 level to conclude that at least one type of defect occur in different proportion