Proceso DMAIC de Six Sigma - Fase Controlar - Selección de cartas de control

Tenga en cuenta estos puntos al seleccionar una carta de control:

Datos de variables: para observaciones numéricas individuales, utilice una carta de individuales y rango móvil (I-MR) cuando corresponda. Para subgrupos racionales, una carta Xbar sigue sus medias, mientras que una carta R (rango) o S (desviación estándar) sigue la dispersión dentro de ellos. El diagrama utiliza Xbar-R para tamaños de subgrupo de 2–8 y Xbar-S para 9 o más; es una orientación, no un umbral universal.

Datos por atributos: distinga primero las unidades no conformes (defectuosas) de las no conformidades (defectos). Para unidades, una carta np muestra la cantidad cuando el tamaño del subgrupo es fijo; una carta p muestra la proporción y admite tamaños variables. Para defectos, una carta c muestra cantidades con iguales oportunidades de inspección; una carta u muestra defectos por unidad y admite exposiciones variables. Las cartas p y u también pueden utilizarse con tamaño de subgrupo o exposición fijos. Compruebe que los supuestos de muestreo y distribución sean adecuados para el proceso.

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Guía de selección de cartas de control de Six Sigma

Situation	Example	Statistical Test
Continuous data, one figure at a time	For example: A team is tracking the length of time, measured in days, it takes to process claims. They are randomly selecting one completed claim each day and plotting the time it took to complete that one claim.	Individuals and Moving Range I & MR Chart
Continuous data, averages with small sub-group sizes	For example: A team is tracking cycle time, measured in days, for claims processing. They are randomly selecting five completed claims each day and plotting the average cycle time.	Average and Range X bar & R Chart
Continuous data, averages with large sub-group sizes	For example: A process owner is monitoring call length, measured in minutes and seconds. Each day, the average length for all calls received is plotted. The call center receives over 100 calls per day.	Average and Standard Deviation X bar & S Chart

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Selección de cartas de control de Six Sigma – Y continua

Situation	Example	Statistical Test
Discrete data, measuring defects with a constant sample size	For example: A team is tracking the number of incomplete fields on applications. Each day, they pull a random sample of fifty applications and review them for completeness. They plot the total number of fields that are incomplete.	Number of Defects (c Chart)
Discrete data, measuring defects with a variable sample size	For example: Another process owner is tracking the number of fields that are incomplete in applications. Each day her team reviews all incoming applications for completeness and plots the number of incomplete fields per number of applications.	Number of Defects per Unit (u Chart)
Discrete data, measuring defective units with a constant sample size	For example: A team is tracking the number of applications that come in with incomplete information. Each day, they pull a random sample of fifty applications and review them for completeness. They plot the number that are incomplete.	Number Defective (np Chart)
Discrete data, measuring defective units with a variable sample size	For example: A team is tracking the number of applications that come in with incomplete information. Each day, they review all applications for completeness and plot the percent that are incomplete.	Fraction Defective (p Chart)

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Selección de cartas de control de Six Sigma – Y discreta