An experiment was conducted to compare the mean number of tapeworms in the stomachs of sheep that had been treated for worms against the mean number in those that were untreated. A sample of 14 worm-infected lambs was randomly divided into 2 groups. Seven were injected with the drug and the remainders were left untreated. After a 6-month period, the lambs were slaughtered and the following worm counts were recorded: Drug-treated sheep 18 43 28 50 16 32 13
Untreated Sheep 40 54 26 63 21 37 39

Required:
Test a hypothesis that there is no difference in the mean number of worms between treated and untreated lambs. Assume that the drug cannot increase the number of worms and hence use the alternative hypothesis that the mean for treated lambs is less than the mean for untreated lambs. Use α=0.01.