chapter  9
6 Pages

Mean values

Ifwehaveasetofvaluesofsomequantitythentheaverage,or mean,valueisthesumofthesetofvaluesdividedbythenumber ofquantitiesintheset.Forexample,iftheresistanceoffour resistorsis10.0n,10.4n,10.2nand10.6n,thenthemean valueoftheresistanceis

meanresistance=10·0+10·4 :10·2+10·6=10.3n

Nowsupposewehaveacurrentiwhichvariescontinuously withtimet,i.e.thecurrentisafunctionoftimei=j(t},andwe requirethemeanvalueofthecurrentoversometimeinterval.We canobtainthemeanvalueinasimilarwaytothemeanvalueofthe discreteresistances.Allweneedtodoistakethevaluesofthe currentatanumberofinstancesduringthetimeintervalanddivide thesumofthecurrentvaluesbythenumberofvaluesconsidered. Ingeneral,wewouldexpecttoimprovetheaccuracyofthemean bytakingalargenumberofcurrentvaluessincethenwewouldbe lesslikelytomissanycurrentfluctuationsandnottaketheminto account.