116 



COMPARISONS OF RESPIRATORY EXCHANGE. 



results from this point of view shows that the measured respiratory 

 exchange was practically the same with both forms of the respiration 

 apparatus. 



TABLE 16. Variations of at>erage results obtained ivith the tension-equalizer unit from those 

 obtained unth the spirometer unit. 



In considering the statistics of the individual periods, it is of interest 

 to calculate the percentage uniformity of results obtained with the 

 two apparatus. The results of such a calculation are best shown by 

 probability curves which have been plotted from data obtained in the 

 following manner: 



The difference between the results for an individual period and the 

 average for the apparatus on that day was first found; this difference 

 when divided by the average result obtained with the apparatus in 

 that experiment gave the percentage variation for the period. The 

 percentage number of periods varying more than 0.5 per cent from the 

 average results was then found by determining the number of periods 

 showing this variation and dividing this number by the total number of 

 periods. 



For example, in the experiment with H. B. L. on March 5, the differ- 

 ence between the carbon-dioxide elimination for the first period with the 

 tension-equalizer unit (218 c.c.) and the average carbon-dioxide elimi- 

 nation with that apparatus for the day (214 c.c.) was 4 c.c.; this 

 divided by the average carbon-dioxide elimination (214 c.c.) gives, 

 as the percentage variation for that period, 1.87 per cent. With the 

 tension-equalizer unit there were 26 periods in which the carbon-diox- 

 ide elimination varied more than 0.5 per cent from the average of the 

 carbon-dioxide elimination with this apparatus. This number of 

 periods divided by the total number of periods (30) gives 87 per cent 

 as the percentage number of periods with the tension-equalizer unit 

 varying more than 0.5 per cent from the grand average of the carbon- 

 dioxide elimination. 



