Six sigma school problem help. I need help with a CCR and CTQ along with creatin
ID: 3301993 • Letter: S
Question
Six sigma school problem help.
I need help with a CCR and CTQ along with creating a measurement system using gauge R&R or six sigma.
(prentend problems I am creating for a fake restraurant)
I need to create a measure phase “as is” process map, with output, input, and process indicators
Issues I created that need to be addressed
*multiply times to get through the to place a order. I want not more then 2 rings baseline will be 3
*15-20mins is told when placing order it is never 15-20 mins I always have to wait an additional 20 minutes. I want a cycetime of 20-25mins baseline 30mins
*wrong order 1 out of every 5 orders = communication I want no wrong order
I need to create a sigma score.
I need state a statistical hypothesis to test (H0) and the alternative hypothesis (H1).
I need to apply a equation like this to help with the above measuring Inventory = X widgets, Processing Time = X minutes/widget, Defect Rate = P%).
Explanation / Answer
Hello,
As I understand from the given information, following queries needs to be answered:
Create an As-Is map for the hypothetical restaurant problem
Current Issues to be Quantified using Sigma Score & other ways
Overall Lead Time to receive the order
Wrong Order i.e. Wrong item Received
Hypothesis test to be done
Answer
As Is Process Map – A simple SIPOC can be prepared for the given problem as mentioned below. For the process indicators please refer point (2)
Supplier (S)
Inputs (I)
Process (P)
Output (O)
Customer (C)
Order Processing Team
Order
Order is Received from Customer (Step1)
Package containing Ordered food Item
Customer
Cook
Material
Order is forwarded to the Kitchen (Step2)
Delivery Team
Item is Prepared (Step3)
Item is matched with the Order & Packed (Step4)
Package is Given to the Delivery Team along with Address (Step5)
Package is Shipped to Customer (Step6)
2. Quantification of Process Indicators using Sigma
Overall Waiting Time
As shown in the SIPOC above, the process consists of 6 steps. Please note that processing time involved in each of the steps is called Cycle Time (CT). Overall time it takes to deliver the item from the instance, order is placed is called Lead Time (LT). Hence Lead Time is equal to the sum of Cycle Times of Each Step & Waiting time in between the steps.
i.e. LT = CT(Step1) + CT(Step2) + CT(Step3) + CT(Step4) + CT(Step5) + CT(Step6) + Waiting Time.
In order to calculate the sigma of overall Lead Time, please follow the steps mentioned below:
Let is assume you observe 10 transactions.
Calculate the Lead Time for each transaction. Let us assume Average Lead Time is 15 min.
Determine the acceptable time as per the customer (This is also called as Specification Limit & in this case the Specification Limit will be one sided i.e. only Upper Specification Limit is relevant here). Let’s assume that the Upper Specification Limit (USL) is 20 min.
Calculate the Lead Time Standard Deviation as below
Square Root [Summation{(Lead Time of Transaction(i) – Average Lead Time)}/(Number of Transactions -1)]
Let us say you observed 10 transactions. The above formula will become – Square Root [Summation{(Lead Time of Transaction(i) – Average Lead Time)}/(9)]
You may also use STDEV.S function in excel.
After Calculating the Lead Time Standard Deviation use the following formula
Long Term Sigma Score = (USL – Average Lead Time)/Standard Deviation i.e. {(20 – 15)/SD}
Short Term Sigma Score = Long Term Sigma + 1.5
(Generally Short Term Sigma is reported for the process, here 1.5 is a standard Sigma Shift)
(b) Incorrect Order Received.
In this case you need to use DPMO (Defects Per Million Opportunity) as given below:
Let us say you observed 50 transactions. Let us also assume that, the ways a transaction can go wrong are 2 i.e. Order Exchanged with Other & Partial Order Received. These are called opportunities. Let us say 4 out of 50 transactions were defectives with 2 Defects in each transaction.
DPMO = {(Number of Defects) / (Total Number of Transactions * Opportunities)}* 1000000. In this example DPMO = {(8)/(50*2)}*1000000 = 80000
For the given DPMO, refer to the associated sigma level using Sigma Chart which you can easily find on the internet.
(C) In general you may also report the CTQ’s as Lead Time = 20 Min / Transaction or Defects 4 / Transaction without associated Sigma Level.
3. Hypothesis Testing
In order to compare Pre & Post Performance of the process, you must use Two Sample T Test. Please ensure you take more than 30 observations as it will make the test robust against non normality assumption. You may use Excel Analysis Toolpack to do the test automatically or use the following steps:
Set the Hypotheses. H0 (Null Hypothesis – No Difference between the two measures i.e. Pre & Post Average Lead Time)
H1 (Alternate Hypothesis) – Post Average Lead Time is Lower Then Pre Average Lead Time.
Find the Difference Between Pre & Post Average Lead Time (D = Pre Average Lead Time – Post Average Lead Time)
Assuming that the process has constant variance divide the difference (D) by Standard Error (SE = SD/Number of Transactions).
Use standard t distribution chart for one sided test to find the associated p value. Use degree of freedom equal to Number or Transactions -1.
Compare the p value with calculated statistic in step 2. If tabulated value is less than calculated value Reject Null Hypothesis else fail to Reject Null Hypothesis.
Supplier (S)
Inputs (I)
Process (P)
Output (O)
Customer (C)
Order Processing Team
Order
Order is Received from Customer (Step1)
Package containing Ordered food Item
Customer
Cook
Material
Order is forwarded to the Kitchen (Step2)
Delivery Team
Item is Prepared (Step3)
Item is matched with the Order & Packed (Step4)
Package is Given to the Delivery Team along with Address (Step5)
Package is Shipped to Customer (Step6)
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