Proses DMAIC Six Sigma - Tahap Control - Pemilihan Diagram Kendali

Ingat hal-hal berikut saat memilih diagram kendali:

Data variabel: Untuk pengamatan numerik individual, gunakan diagram individu dan rentang bergerak (I-MR) jika sesuai. Untuk subgrup rasional, diagram Xbar memantau rata-rata subgrup, sedangkan diagram R (rentang) atau S (simpangan baku) memantau sebaran di dalam subgrup. Diagram ini menggunakan Xbar-R untuk ukuran subgrup 2–8 dan Xbar-S untuk 9 atau lebih; ini merupakan panduan pemilihan, bukan batas yang berlaku universal.

Data atribut: Pertama, bedakan unit yang tidak sesuai (cacat) dari ketidaksesuaian (cacat). Untuk unit, diagram np menunjukkan jumlah unit cacat ketika ukuran subgrup tetap; diagram p menunjukkan proporsinya dan dapat mengakomodasi ukuran subgrup yang berubah. Untuk cacat, diagram c menunjukkan jumlah cacat pada kesempatan inspeksi yang sama; diagram u menunjukkan cacat per unit dan mengakomodasi paparan yang berubah. Diagram p atau u juga dapat digunakan ketika ukuran subgrup atau paparan tetap. Periksa apakah asumsi pengambilan sampel dan distribusi sesuai dengan proses.

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Panduan Pemilihan Diagram Kendali 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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Pemilihan Diagram Kendali Six Sigma – Y Kontinu

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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Pemilihan Diagram Kendali Six Sigma – Y Diskret