152 SAMPLING FROM BINOMIAL POPULATIONS Ch. 5 



Assuming that b can be done, which method of sampling, if either, do you 

 recommend as statistically best? Why? Can you suggest a better method 

 than either of these? 



12. Referring to the situation of problem 11, suppose that the true proportion 

 of rainbow trout is .40 and that 8 per cent of the rainbows in this area are 

 known to be afflicted with a certain disease. What is the probability that a 

 trout caught at random is a rainbow trout without the disease? Ans. P = .37. 



13. Referring again to problem 11, assume that 60 per cent of the trout in 

 another stream in this same region are brook trout. If on a random sample of 

 50, 22 are brook trout and the other 28 are rainbows, would you accept or reject 

 the hypothesis that p = .60 for brook trout in this stream? Explain. 



14. Suppose that there are two mountain streams which run quite close to- 

 gether in a certain area but whose head waters are far apart. You wish to 

 know if the trout populations of these two streams are the same, in a certain 

 well-defined area, as regards proportions of the four species: rainbow, cutthroat, 

 brook, and dolly varden trout. Given the following random sampling data, 

 what would you conclude? 



Number of Trout 

 Rain- Cut- Dolly 



bow Brook throat Varden Sum 



Stream 1 73 68 49 10 200 



Stream 2 70 85 80 15 250 



Sum 143 153 129 25 450 



Ans. Chi-square = 5.65 3D/F, P S .13 



15. Referring to problem 14, compute and interpret the CI 95 on the true per- 

 centage of brook trout in stream 2. 



REFERENCES 



Dixon, Wilfrid J., and Frank J. Massey, Jr., Introduction to Statistical Analysis, 



McGraw-Hill Book Company, New York, 1951. 

 Grant, Eugene L., Statistical Quality Control, Second Edition. McGraw-Hill 



Book Company, New York, 1952. 

 Neyman, Jerzy, First Course in Probability and Statistics, Henry Holt and 



Company, New York, 1950. 

 Snedecor, George W., Statistical Methods Applied to Experiments in Agriculture 



and Biology, Fourth Edition, Iowa State College Press. Ames, Iowa, 1946. 

 Tippett, L. H. C, Technological Applications of Statistics, John Wiley and Sons, 



New York, 1950. 



