Question

A sales consultant for Herron Pharmaceuticals wished to confirm that their packet of 24 paracetamol tablets was cheaper at the retail level than their rival product. The sales consultant collected price data from two independent samples, of size 22 for Herron and 28 for the rival company. These yielded an average and variance for the retail price of Herron's product of 380 cents and 93 cents squared respectively, and 382 cents and 60 cents squared for the rival. Under the usual assumptions, determine a 90% confidence interval for the price difference (use Herron minus rival) stating only the upper limit of the interval in cents (round to the nearest whole number).

Answer 1

standard error se=√(S21/n1+S22/n2)=

2.524

Point estimate of differnce =x1-x2=			-2.000
for 90 % CI & 39 df value of t=			1.6850
margin of error E=t*std error   =			4.253
lower bound=mean difference-E=			-6.253
Upper bound=mean differnce +E=			2.253

from above, upper limit of the 90% confidence interval =2 cents