Ch. 5 REVIEW PROBLEMS 151 



4. The prices of barley in the North Central States during 1945 are given 

 below in cents. (Agricultural Statistics, 1946, USDA.) Compute two different 

 averages of these prices and discuss their meanings and their limitations. 



State: Ohio Indiana Illinois Michigan Wisconsin Iowa Minnesota 

 Price: 106 111 111 118 119 103 107 



State: Missouri N. Dakota S. Dakota Nebraska Kansas 

 Price: 116 102 103 96 97 



5. Determine and interpret the coefficient of variation for the prices of 

 problem 4. 



6. Calculate the mean deviation for the prices of problem 4 and discuss its 

 meaning. Ans. AD = 6.32. 



7. If the egg weights for Rhode Island Red hens are considered to be nor- 

 mally distributed with n = 60.5 grams and a — 4.0 grams, what range of egg 

 weights would you expect to include the middle 90 per cent of all weights? 



8. The following table (taken from A. S. Weiner, Blood Groups and Trans- 

 fusions, Thomas, with the consent of the author and the publisher) records the 

 results of a study of the inheritance of the P factor. 



* Definite doubt established regarding legitimacy. 



Recalling that P+ is genetically PP or Pp, and that P— is only pp, test 

 statistically the agreement between the above data on children's blood types 

 and the numbers expected if P-f- is assumed to be Pp twice as frequently as it 

 is PP. Consider the (4) * entry as zero. 



Ans. Pj(x 2 ^0.33) >.53; P 2 ( x 2 ^5.57) = .018 

 on P+ X P+ and P+ X P-, respectively. 



9. Make up a set of numbers which has an arithmetic mean of 10 and a 

 standard deviation of 2. 



10. Is there any evidence in the table of problem 8 for or against the assump- 

 tion that P+ = Pp twice as frequently as P+ = PP? Explain. 



11. Suppose that a large, deep pool in a mountain stream contains a great 

 many trout of just two kinds, rainbow and brook. You wish to leam what 

 percentage are rainbows. Two methods of sampling have been suggested thus 

 far. 



(a) Fish the pool until 50 trout are caught, and then use this sample evidence 

 as the basis for estimating p. 



(b) Devise a trap into which the trout will go and be caught, and secure a 

 sample of 50 this way. 



