Parts Manufactured by an Injection Molding Process Are Subjected to a Compressive

question 65

Multiple Choice

Parts manufactured by an injection molding process are subjected to a compressive strength test.We monitor the compressive strength of the parts manufactured by this process using an and an s control chart.Samples of size 9 are taken at regular intervals,and their mean compressive strength (in psi = pounds per square inch) and standard deviation are plotted on the charts in time order.The overall mean of the sample means is = 81.2 psi,and the sample standard deviation of all measurements is s = 3.0 psi.Specifications call for the compressive strength of parts to be 80 ± 2.5 psi.The control chart constants are (partially) reproduced below. What is the value of an estimate of the capability index C_p?

• A)0.140
• B)0.144
• C)0.269
• D)0.278

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Definitions:

Straight Line

In mathematics and statistics, a linear relationship or function that can be graphically represented as a straight line in Cartesian coordinates.

Correlation Coefficient

A statistical measure ranging from -1 to 1 that indicates the strength and direction of the linear relationship between two variables.

Scatterplot

A graphical representation of individual data points plotted on a two-dimensional plane, often used to observe and analyze the relationship between two variables.

Least Squares Regression Line

A straight line that best fits the data on a scatter plot, minimizing the sum of the squares of the vertical distances of the points from the line.