ICGB Iassc Certified Lean Six Sigma Green Belt Practice Questions

In the Y = f(x) relationship, Y is the output or effect (the problem being measured), and the 'x's are the inputs or causes that influence the output. The number of invoice errors (Y) is a function of various inputs (x's). The level of training is a potential input or cause (an 'x') that could directly impact the error rate. The other options are all different ways of measuring the output (Y) or consequences of the output.

This statement is true. Cp measures the potential capability of a process, assuming it is perfectly centered. It compares the process spread to the specification spread. Cpk measures the actual capability, taking the process centering into account. A large gap between a high Cp and a low Cpk means the process has low variation (good potential) but is not centered correctly within the specification limits, causing defects on one side.

The waste of Motion refers to any movement of people or equipment that does not add value to the product or service. The operator walking to get tools is a classic example of unnecessary motion. Transportation waste, by contrast, refers to the movement of the product or materials themselves, not the operator.

While multiple regression on historical data could provide some insights, it is often plagued by confounding variables and may not reveal interactions. A Design of Experiments (DOE) is the most powerful and efficient tool for this situation. DOE allows the team to systematically and simultaneously change the settings of multiple input factors (supplier, speed, temperature) to determine their individual effects (main effects) and their combined effects (interaction effects) on the output (concentration). This active, planned experimentation is far more effective than passive data analysis for optimizing a process.

The Chi-Squared test of independence is used to determine if there is a significant association between two categorical variables. In this scenario, 'Shift' is one categorical variable with three levels, and 'Type of Error' is another categorical variable with three levels. A contingency table would be created to show the frequencies of each error type on each shift, and the Chi-Squared test would assess whether the observed frequencies differ significantly from what would be expected if there were no relationship between the variables.

SIPOC stands for Suppliers, Inputs, Process, Outputs, and Customers. Its primary purpose is to provide a simple, high-level map of a process from beginning to end. This helps the project team agree on the project's boundaries (start and end points), identify key stakeholders (suppliers and customers), and ensure everyone has a common understanding of the process before diving into detailed mapping and analysis.

A %Study Variation of 45% indicates an unacceptable measurement system. Any conclusions drawn from data collected with this system would be invalid. The principle is 'fix the measurement system before analyzing the process'. Since the primary issue is reproducibility between shifts, the most critical action is to standardize the process and retrain the operators. Only after the measurement system is proven to be reliable (typically <30% study variation) can the team confidently proceed with data collection and analysis.

The 2-sample t-test assumes that the data is normally distributed. Since the data is highly skewed, this assumption is violated, making the t-test results unreliable. The Mann-Whitney test is a non-parametric alternative that does not require normality and tests for a difference in medians, which is a more robust measure of central tendency for skewed data. Therefore, the conclusion should be based on the Mann-Whitney test, which indicates a significant difference (p < 0.05).

An I-MR (Individuals and Moving Range) chart is designed for continuous (variable) data where measurements are taken one at a time, making the logical subgroup size one. In this scenario, viscosity is a continuous measurement, and only one reading is taken per batch. Therefore, the I-MR chart is the most appropriate choice to monitor the process mean and variation between batches.

The Risk Priority Number (RPN) is calculated by multiplying the scores for Severity, Occurrence, and Detection (S x O x D). In this case, RPN = 8 x 3 x 7 = 168. The RPN is not an absolute measure but a relative one, used to rank and prioritize potential failure modes. Teams use the RPN to focus their limited resources on mitigating the highest-risk items first.