VALIDITY OF THE SURVEY METHOD OF RESEARCH. 



13 



nearly the same as on the corresponding full pages. Thus, in the 

 case of the drill press the third page contains only 44 replies, but the 

 percentage of owners among them is nearly the same as on the pre- 

 ceding full page. Even here the number of replies is sufficient to 

 permit the law of chance to make itself evident. 



Table IX. — Illustrating operation of law of chance. 



Implement. 



No. 



Number 

 of farms 

 having. 



Percent- 

 age of 

 owners 

 on two 

 pages. 



Number 

 of farms 

 recom- 

 mending 



Per cent 

 of those 

 recom- 

 mending 

 having. 



Carborundum or emery wheel 



Set of stocks and dies 



Gasoline blowtorch 



Wrecking tool 



Pinch bar 



Hack saw 



Small hoist 



Drill press, or breast drill 



Combination vise, drill, and anvil 

 Combination pliers 



Expansion bit 



Combination bevel square 



Heary shears, or tinner's snips. . . 



48S 

 369 

 367 

 5 

 205 

 105 

 537 

 532 

 133 

 612 

 598 



87 

 478 

 450 



38 

 520 

 519 

 148 

 454 

 420 



26 

 370 

 345 

 638 

 634 

 190 

 349 

 296 

 375 

 274 

 448 

 425 



53 



50.00 

 50.00 

 50.14 



50.3 



49.7 



50.5 

 49.5 



51.5 

 48.5 



50.1 



52.0 

 48.0 



50.15 

 49.85 



51.32 



700 

 700 

 700 

 700 

 6 

 700 

 426 

 700 

 700 

 180 

 700 

 700 

 104 

 700 

 700 



53 

 700 

 700 

 220 

 700 

 700 



44 

 700 

 654 

 700 

 700 

 216 

 700 

 568 

 700 

 494 

 700 

 700 



86 



69.71 

 69.71 

 52.71 

 52.43 



29.28 

 24.64 

 76.71 

 76.00 

 73.88 

 87.43 

 85.43 

 83.65 

 68.28 

 64.28 

 71.69 

 74.28 

 74.14 

 67.27 

 64.85 

 60.00 

 59.09 

 52.85 

 52.75 

 91.14 

 90. 57 

 87.96 

 49.86 

 52.11 

 53.57 

 55. 46 

 64.00 

 60.71 

 61.62 



The fact that in each case" it is page 1 that has the highest propor- 

 tion of owners is of no significance, since the full pages were deliber- 

 ately arranged in this order after the tabulation was completed, the 

 original chance arrangement being thus lost. 



MISTAKEN NOTIONS OF ACCURACY. 



In the endeavor to find the average value of a variable quantity, 

 such as annual rainfall, the yield per acre of a crop under given con- 

 ditions, etc., there is such a thing as gross inaccuracy in the final re- 

 sult even where the individual measures are made with a high degree 

 of precision. Suppose, for instance, it is desired to ascertain the 

 average yield of winter wheat after summer fallow as compared with 

 the yield after a preceding crop of small grain, under the soil and 

 climatic conditions prevailing on a particular tract of uniform soil. 



