planLTPD {LTPDvar}

Calculation of LTPD plan for sampling inspection by variables

Description

Calculation of LTPD plan (sample size n and critical value k) for sampling inspection by variables

Usage

planLTPD(N, pt, pbar, b = 0.1, cm = 1,method = c("exact", "napprox","ewma2","ewmaSK" ),
intdif = 20,lam=1)

Arguments

N

lot size (number of items in the lot)

pt

lot tolerance fraction defective

pbar

process average fraction defective

b

probability of accepting a lot of tolerance quality pt (consumer risk), default value 0.1

cm

parameter used in cost function of plans (see Ims) and defined as cost of inspection of one item by variables divided by cost of inspection of the item by attributes, default value 1

method

type of OC (operating characteristic) used, either "exact" (default) using non-central t-distribution, or "napprox" for approximate OC; if EWMA statistic is to be used, "ewmaSK" stands for the sigma known case, "ewma2" stands for the sigma unknown case

intdif

parameter used in finding n when method other than "napprox", controlling the width of interval to be searched in for sampling plan optimal w.r.t. cost, difference from interval centre (n resulting from planLTPD(..., method = "napprox") to lower or upper bound, default value 20

lam

smoothing parameter in case that EWMA statistic is used

Value

An instance of ACSPlan-class, with sample size in slot n and critical value in slot k.

References

Klufa, J.: Exact calculation of the Dodge-Romig LTPD single sampling plans for inspection by variables. Statistical Papers, Springer, Vol. 51(2), pages 297-305, 2010.

See Also

LTPDvar-package, OC, ACSPlan-class, Ims

Examples

# find LTPD plan
planLTPD(N=1000,pt=0.1,pbar=0.001);
planLTPD(1000, 0.01,0.001,cm=1.5,b=0.1,method="ewmaSK",lam=0.9,intdif=60);
planLTPD(1000, 0.01,0.001,cm=1.5,b=0.1,method="ewma2",lam=0.9);