for 75 per cent apparent attack were obtained, will facilitate under- 

 standing of the table, and the underlying problems. 



The first column shows the apparent percentage. This is done, 

 because in practice one will start from a sample of picked cotton, 

 and require to know how much loss of cotton there was in the crop 

 to which it belonged. The corresponding true percentage, supposing 

 four worms to be the average maximum number of worms found in 

 a pickable boil has been calculated in the same way as Table I (eleven 

 sound bolls, 9-79 with one, 8-71 with two, 7-75 with three, 6-90 with 

 four worms, together 44-15 bolls of which eleven sound giving approxi- 

 mately 75 per cent attack. 



The third column showing the number of worms per 100 bolls 

 of the apparent sample has been calculated from the same set of figures, 

 as follows : 



but as this represents only 44-15 bolls in all, the number must be 

 increased to bring the bolls up to 100, giving consequently about 

 176 worms. 



The fourth column is intended to show the proportion of the 

 entire boll population not included in the select population. As only 

 forty-four bolls were included in the select population fifty-six must 

 be excluded and represent total loss. 



The fifth column shows the loss within the select population. 

 It has been shown on Table V that the amount of loss caused by a 

 single worm approximates to about one tenth of a boll (Sakellarides). 

 One hundred bolls with apparent percentage 75 per cent would thus 

 normally have lost 17-6 per cent of their substance (or from observation 

 17-1 per cent). But as we are calculating total loss of the entire 

 population in percentages, we can only put into the table 44 per 

 cent of 17-6 per cent, which gives about 8 per cent. 



In the sixth column the losses entered in the fourth and fifth 

 columns have been combined to give the probable true loss over the 

 whole boll population. 



It is of importance to remember : 



(a) That the percentage attack found when examining samples 

 of open pickable bolls is nearly always an apparent one. 



(b) That when they differ the true percentage attack is always 

 higher than the apparent percentage. 



(c) That the higher the percentage of attack the greater the 

 difference of the apparent from the true percentage attack. 



