Gráfico Tipo C Control Estadístico del Proceso.

Sandra Elisa Reyes Velázquez UNIVERSIDAD TECNOLÓGICA DE TORREÓN.

Gráfico Tipo C

Ejemplo:

En una empresa fabricante de motores, se busca medir la cantidad de

defectos que se presentan en las unidades terminadas: Para lo cual se

obtiene una muestra de 40 unidades y se anotan los resultados, los cuales

son los siguientes:

Inciso a Se pasa hacer los cálculos necesarios con las siguientes fórmulas, para hacer

el gráfico:

Instrucciones:

a) Realizar un gráfico de

control

tipo C con la ayuda de Excel

b) Identificar las Nelson Rules

que

aparecen en el gráfico.

UCL 21.2037088

CL 11.175

3.34290293

LCL 1.14629121

n Defectos n Defectos

1 21 21 3

2 22 22 10

3 9 23 12

4 12 24 17

5 15 25 15

6 8 26 6

7 14 27 16

8 9 28 15

9 13 29 4

10 6 30 8

11 19 31 8

12 17 32 9

13 21 33 10

14 7 34 7

15 10 35 6

16 8 36 21

17 11 37 12

18 6 38 15

19 4 39 6

20 6 40 9

Se hace el siguiente formato en Excel para poder hacer la gráfica:

n Defectos C C+1 C+2 C+3 C+1 C+2 C+3

1 21 11.175 14.5179029 17.8608059 21.2037088 7.83209707 4.48919414 1.14629121

2 22 11.175 14.5179029 17.8608059 21.2037088 7.83209707 4.48919414 1.14629121

3 9 11.175 14.5179029 17.8608059 21.2037088 7.83209707 4.48919414 1.14629121

4 12 11.175 14.5179029 17.8608059 21.2037088 7.83209707 4.48919414 1.14629121

5 15 11.175 14.5179029 17.8608059 21.2037088 7.83209707 4.48919414 1.14629121

6 8 11.175 14.5179029 17.8608059 21.2037088 7.83209707 4.48919414 1.14629121

7 14 11.175 14.5179029 17.8608059 21.2037088 7.83209707 4.48919414 1.14629121

8 9 11.175 14.5179029 17.8608059 21.2037088 7.83209707 4.48919414 1.14629121

9 13 11.175 14.5179029 17.8608059 21.2037088 7.83209707 4.48919414 1.14629121

10 6 11.175 14.5179029 17.8608059 21.2037088 7.83209707 4.48919414 1.14629121

11 19 11.175 14.5179029 17.8608059 21.2037088 7.83209707 4.48919414 1.14629121

12 17 11.175 14.5179029 17.8608059 21.2037088 7.83209707 4.48919414 1.14629121

13 21 11.175 14.5179029 17.8608059 21.2037088 7.83209707 4.48919414 1.14629121

14 7 11.175 14.5179029 17.8608059 21.2037088 7.83209707 4.48919414 1.14629121

15 10 11.175 14.5179029 17.8608059 21.2037088 7.83209707 4.48919414 1.14629121

16 8 11.175 14.5179029 17.8608059 21.2037088 7.83209707 4.48919414 1.14629121

17 11 11.175 14.5179029 17.8608059 21.2037088 7.83209707 4.48919414 1.14629121

18 6 11.175 14.5179029 17.8608059 21.2037088 7.83209707 4.48919414 1.14629121

19 4 11.175 14.5179029 17.8608059 21.2037088 7.83209707 4.48919414 1.14629121

20 6 11.175 14.5179029 17.8608059 21.2037088 7.83209707 4.48919414 1.14629121

21 3 11.175 14.5179029 17.8608059 21.2037088 7.83209707 4.48919414 1.14629121

22 10 11.175 14.5179029 17.8608059 21.2037088 7.83209707 4.48919414 1.14629121

23 12 11.175 14.5179029 17.8608059 21.2037088 7.83209707 4.48919414 1.14629121

24 17 11.175 14.5179029 17.8608059 21.2037088 7.83209707 4.48919414 1.14629121

25 15 11.175 14.5179029 17.8608059 21.2037088 7.83209707 4.48919414 1.14629121

26 6 11.175 14.5179029 17.8608059 21.2037088 7.83209707 4.48919414 1.14629121

27 16 11.175 14.5179029 17.8608059 21.2037088 7.83209707 4.48919414 1.14629121

28 15 11.175 14.5179029 17.8608059 21.2037088 7.83209707 4.48919414 1.14629121

29 4 11.175 14.5179029 17.8608059 21.2037088 7.83209707 4.48919414 1.14629121

30 8 11.175 14.5179029 17.8608059 21.2037088 7.83209707 4.48919414 1.14629121

31 8 11.175 14.5179029 17.8608059 21.2037088 7.83209707 4.48919414 1.14629121

32 9 11.175 14.5179029 17.8608059 21.2037088 7.83209707 4.48919414 1.14629121

33 10 11.175 14.5179029 17.8608059 21.2037088 7.83209707 4.48919414 1.14629121

34 7 11.175 14.5179029 17.8608059 21.2037088 7.83209707 4.48919414 1.14629121

35 6 11.175 14.5179029 17.8608059 21.2037088 7.83209707 4.48919414 1.14629121

36 21 11.175 14.5179029 17.8608059 21.2037088 7.83209707 4.48919414 1.14629121

37 12 11.175 14.5179029 17.8608059 21.2037088 7.83209707 4.48919414 1.14629121

38 15 11.175 14.5179029 17.8608059 21.2037088 7.83209707 4.48919414 1.14629121

39 6 11.175 14.5179029 17.8608059 21.2037088 7.83209707 4.48919414 1.14629121

40 9 11.175 14.5179029 17.8608059 21.2037088 7.83209707 4.48919414 1.14629121

C= 11.175

S= 3.34290293

Gráfico de control de no conformidad

Inciso b Identificación de las Nelson Rules:

Rule 1:

One point is more than 3 standard deviations from the mean.

Rule 2

Nine (or more) points in a row are on the same side of the mean.

Rule 4

Fourteen (or more) points in a row alternate in direction, increasing then

decreasing

Rule 5

Two (or three) out of three points in a row are more than 2 standard

deviations from the mean in the same direction

Rule 6

Four (or five) out of five points in a row are more than 1 standard deviation

from the mean in the same direction.