STUDENT CODE NO.............................................................................

STUDENT'S SIGNATURE ....................................................................

DATE SUBMITTED.................................................................................

email.............................................................

MODULE TITLE : STATISTICAL PROCESS CONTROL

TOPIC TITLE : INSPECTION AND SAMPLING; FURTHER TOPICS

TUTOR MARKED ASSIGNMENT

NAME ............................................................................................................................. ........................................... ............

ADDRESS ............................................................................................................. .............................................................. . ............................................................................................................................. ....................................................................... . ............................................................................................................................. ....................................................................... .. ........................................................................ HOME TELEPHONE ......................................................................

SPC - 4, 5 – TMA v2.1

© University of Teesside 2016

1

1. (a) Components are being made in batches of 400, and Inspection Level II is required. Using TABLE 1, determine the BS 6001 code letter.

(b) From your answer to part (a) of this question, and using TABLE 3, determine the sample size that should be drawn.

(c) If an AQL of 2.5 is specified, use TABLE 3 to determine the acceptance

and rejection levels applying.

(d) If we assume a 5% defectives level, use FIGURE 1 to determine the percentage of lots we can expect to be accepted.

2. The process for the production of an electrical device is suitable for inspection by variables. Production is inspected in lots of 150, at inspection level II, normal inspection with AQL = 2.5%. The maximum temperature of operation for the device is specified as 50 °C.

(a) Use TABLES 4 and 5 to find the sample code letter, the sample size and the acceptability constant.

(b) A sample is taken and the temperature measurements are as follows:

43 °C, 49 °C, 46 °C, 39 °C, 44 °C, 45 °C, 40 °C, 48 °C, 46 °C and 41 °C.

Determine whether the lot should be accepted.

3. Consider the following scenario:

A manufacturer makes silicon strain gauge transducers that are designed to produce a linear voltage output that is directly proportional to the applied pressure. Six different processing lines are used to manufacture the gauges.

In this application an important physical property of the silicon layer formed to fabricate the gauge is its Young’s modulus. There have been some calibration problems with the gauges and an engineer suspects that one of the process lines is producing a mean value of Young’s modulus that is different from that of the other processing lines.

2

The Young’s modulus of the silicon was measured from a random sample of four gauges taken from each of the processing lines. The results [in GPa] are given in the table below.

Your manager asks you to test the engineer’s hypothesis by performing an analysis of variance at the 0.05 level of significance. He has, moreover, heard about ‘Six Sigma’ and asks you to advise if its introduction would alleviate any supposed issues with the manufacturing of the gauges.

Produce a short report to update your manager on both the method and results of your analysis and the introduction od ‘Six Sigma’.

Processing line 1 2 3 4 5 6

175 164 203 146 175 183

169 192 157 167 192 162

158 177 178 208 165 175

186 154 189 189 205 201

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APPENDIX TABLES 1–5

4

5

6

7

8

9