Question

Use only Minitab if you won't use Minitab leave it for another person to work on it please.

The breaking strengths of carbon fibers, which are used in fibrous composite materials, were measured by randomly selecting samples of 5 fibers. See attached data spreadsheet contains the data. a. Form an x-bar/R chart. b. Based on your answer to part a, would you say that the process is in control, or 1. not? Explain your answer. Also, discuss anything unusual that you notice about the process The specifications for this process require that fibers have a breaking stress of at least 1.2 GPa. Does it appear the process meets this requirement? Explain your answer. c. Y5 Y4 Y3 Y2 Subgroup Y1 2.5 2.7 2.9 3.2 1.8 3.0 2.7 2.7 3.3 3.7 3.2 3.2 3.0 2.9 3.3 2.6 2.6 2.8 1.4 1.8 5.6 1.7 3.3 3.8 3.0 3.4 3.3 3.2 2.8 4 2.5 2.8 3.3 2.6 2.9 2.6 2.2 3.0 2.4 9 10 2.8 3.7 4.9 1.6 2.0 1.0 2.8 3.2 1.6 2.2 3.5 1.8 1.6 1.6 1.9 12 13 14 15 16 17 18 19 20 1.7 0.8 1.2 5.1 1.7 3.7 1.2 2.5 1.3 2.5 2.0 1.6 0.9 0.4 2.8 1.1 2.9 2.0 2.8

Answer 1

We will use MINITAB software to get the answers

we will write the data in 5 columns and follow the steps

stat > control charts > variable control chart > X-bar and R chart

a) the X-bar R chart is

Xbar-R Chart of data , %2.63 LCL= 1.301 13 15 17 19 Sample UCL=4.871 4.8 3.6 2.4 R-2.304 1.2-* 0.0 LCL=0 13 15 17 19 Sample

b) at 13th subgroup sample R touches the UCL but did not crossed. hence we ca say all the process in control state.

c) YES. since we can see from the LCL of mean chart is 1.301 so all values at least 1.301 with 95% confidence. hence all values are greater to 1.2 obviously .