Question

An agricultural researcher wanted to investigate the effectiveness of a treatment for tapeworm in the stomach of lambs. 48 tapeworm-infected lambs of approximately the same age and health were randomly divided into two groups. One group of 24 lambs was treated by being dosed with the drug and the remaining group of 24 lambs was left untreated. After a six month period the lambs were killed and the number of tapeworms in each lamb's stomach was recorded. The data are displayed below 43 32 13 38 7 Treated lambs 18 28 50 16 35 33 6 33 36 35 35 24 16 1 36 21 33 38 Untreated lambs 43 22 26 67 52 29 32 42 50 38 28 35 40 54 26 63 21 37 39 23 48 58 28 39 (a) For this study describe the: (i) units (ii) treatment or factor of interest [1 mark (iii) response (b) (i) Use iNZight to draw the appropriate plot(s) for this data set. (You should consider the design of this study to ensure the relevant plot(s) is drawn.) Do not use SPSS to draw the plot(s) (ii) Comment on any features in the plot(s). [1 mark [3 marks Treated.lambs 88 8 8 o O 10 20 30 40 50 Treated.la mbs Untreated.Lambs 8 8 oo o 60 20 30 40 50 Untreated.Lambs

Answer 1

a) i) Units - Number of tapeworms in each lamb's stomach

ii) Treatment or factor of interest - drug dose

iii) Response - Number of tapeworms in the stomach

b) i) The graphs are already given

ii) For the treated lambs we can see that the number of tapeworms present in each lamb's stomach is highly concentrated above 30 thus the drug does not affect much when all the 24 lambs are taken into consideration and the curve is a negatively skewed and the values are mostly between 15 to 35 . In case of the untreated lambs we can see that in most of the lambs the number of tapeworms is more than 30 and nearly all of them are in between 25 to 50 which shows that the drug is still better to use than to be not used. The median value in the latter case is close to 40 which shows that the untreated lambs are in a worse condition than the treated ones.