MILITARY STANDARDS

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Military Standard 105E

Most widely used acceptance sampling system for attributes

MIL STD 105E is Acceptance Sampling System collection of sampling schemes

Can be used with single, double or multiple sampling plans We will consider single sampling plans for this course

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Inspection Types

Normal Inspection Used at start of inspection activity

Tightened Inspection Instituted when vendor’s recent quality history has deteriorated Acceptance requirements for lots are more stringent

Reduced Inspection Instituted when vendor’s recent quality history has been exceptionally

good Sample size is usually smaller than under normal inspection

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Switching Rules

- Production Steady- 10 consecutive lots accepted- Approved by responsible authority

NormalReduced Tightened

- Lot rejected- Irregular production- Lot meets neither accept nor reject criteria- Other conditions warrant return to normal inspection

2 out of 5 consecutive lotsrejected

5 consecutivelots accepted

10 consecutive lots remainon tightened inspection

Start

DiscontinueInspection

AND conditions

OR conditions

Procedure for MIL STD 105E

Choose AQL Choose the inspection level Determine the lot size Find the appropriate sample code size letter from table A-1. Determine the appropriate type of sampling plan to use. Enter appropriate table to find the type of plan to be used. Determine the corresponding normal and reduced inspection

plans to be used when required.

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Example

Suppose product comes from vendor in lots of size 2000 units. The acceptable quality level is 0.65%. Determine the MIL STD 105E acceptance-sampling system.

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Normal Insp. Level

Lot Size

= 2000

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AQL

Plan K

Sample 125 units.

Ac = 2, accept if defects ≤ 2.

Re = 3, reject entire lot if defects ≥ 3.

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AQL

Plan K

Sample 125 units

Ac = 1, accept if defects ≤ 1.

Re = 2, reject entire lot if defects ≥ 2.

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Sample 50 units

Ac = 1, accept if defects ≤ 1.

Re = 3, reject entire lot if defects ≥ 3.

AQL

Plan K

Military Standard 414

MIL STD 414 is a lot-by-lot acceptance-sampling plan for variables introduced in 1957.

Sample sizes are a function of the lot size and the inspection level.

All sampling plans assume the quality characteristic of interest is normally distributed.

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Military Standard 414

MIL STD 414 is divided into four sections: A: general description of the sampling plans including

definitions, sample size code letters, and OC curves for the plans.

B: variables sampling plans based on the sample standard deviation for the case in which the process or lot variability is unknown.

C: variables sampling plans based on the sample range method

D: variables sampling plans for the case where the process standard deviation is known.

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Procedure 1 (k-Method)

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Procedure 2 (M-Method)

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Double specification limit variability unknown

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Example

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Range method for variability unknown

If mentioned in the question then we will go for this method.

In this method all the steps are same as we have done before only difference is instead of calculating standard deviation we will calculate range.

The table used in this method is C1 or C2 and C3 or C4.

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Thank You

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