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

question 10

Multiple Choice

Parts manufactured by an injection molding process are subjected to a compressive strength test.We wish to monitor the compressive strength of the parts manufactured by this process using both and s charts.Samples of size 9 are to be 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 target values for the compressive strengths are a mean of  = 80 psi and a standard deviation of  = 3 psi.The control chart constants are (partially) reproduced below. What is the lower control limit for the
Chart?

• A)71 psi
• B)77 psi
• C)83 psi
• D)89 psi

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Definitions:

Mathematical Formula

A concise way of expressing information symbolically or a rule for calculating numerical values based on certain mathematical operations.

Standard Deviation

A measure of the amount of variation or dispersion of a set of values; a high standard deviation indicates greater variability.

Standard Normal Distribution

A normal distribution with a mean of 0 and a standard deviation of 1, used in z-score calculations to determine probabilities.

Normal Distribution

A statistical distribution which is evenly spread around the mean, indicating that occurrences close to the mean are more common than those further away.