If R is the total resistance of two resistors connected in parallel with resistances R_1 and R_2, then?

R1 = 17 ohms, R2 = 33 ohms

R {nominal} = 17 || 33 = 11.22 ohms

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R1 = 17 ± 3% , therefore R1 = 17 + 3% for maximum and R1 = 17 - 3% for minimum

17 * 0.03 = 0.51 ohms ; 17.51 ohms {maximum} 16.49 ohms {minimum}

R2 = 33 ± 5% therefore R2 = 33 + 5% for maximum and R1 = 33 - 5% for minimum

33 * 0.05 = 1.65 ohms ; 34.65 ohms {maximum} 31.35 ohms {minimum}

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17.51 ohms {maximum} || 34.65 ohms {maximum}

Rmax = 11.6319 ohms

deviation = 11.6319 - 11.22 ohms = +0.4119 ohms

% deviation = +3.6714%

17.51 ohms {maximum} || 31.35 ohms {minimum}

Rmid1 = 11.2349 ohms

deviation = 11.2349 - 11.22 ohms = +0.0149 ohms

% deviation = 0.1330%

16.49 ohms {minimum} || 34.65 ohms {maximum}

Rmid2 = 11.1728 ohms

deviation = 11.1728 - 11.22 ohms = -0.0472 ohms

% deviation = -0.4204%

16.49 ohms {minimum} || 31.35 ohms {minimum}

Rmin = 10.8061 ohms

deviation = 10.8061 - 11.22 ohms = -0.4139 ohms

% deviation = -3.6894%

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Therefore worst case deviation from the nominal value, is when both resistors are at their minimum tolerance.

let

X = R_1 , Y=R_2

1/R = 1/X + 1/Y , differentiate ---> dR/R^2 = dX/X^2 + dY/Y^2

X=17 , Y=33 --->R=11.22

and with dX/X=3% , dY/Y = 5%

--->dR/R = 3.68% , this is maximum error