236 



LINEAR REGRESSION AND CORRELATION 



Ch. 7 



36. Does the concentration of thiamin in raw pork loin increase between the 

 fifty-sixth and the seventy-second week of cold storage (at, or below, 10°F), 

 or is the observed average increase of 10.60 micrograms per gram probably just 

 a sampling accident? Ans. G = 0.221, n = 9, P > .10; sampling accident. 



37. It appears from the sampling data above that the thiamin concentration 

 in raw pork loin decreases during the first 12 weeks of storage, stays about the 

 same through the fifty-sixth week of such storage, and returns to about the 

 original concentration by the end of the seventy-second week of storage. Is 

 this actually the case, according to G-tests, or could the observed results rea- 

 sonably be assigned to sampling error? 



The following data are from the same source as those immediately above, 

 and were taken during the same general experimentation. They record the 

 riboflavin concentration in raw pork loin instead of the thiamin content just 

 studied. These data are to be employed in the solution of problems 38 through 

 43. 



Period of Storage 



12 



(Weeks) 

 24 40 



56 



72 



Mean 2.34 

 range 1 . 85 



3.68 

 0.88 



4.34 

 3.07 



4.60 

 0.98 



4.24 



2.58 



4.70 

 2.00 



38. Make a scatter diagram with Y = mean riboflavin concentration and 

 X = weeks of storage. Is the trend in the bivariate population of X's and Y's 

 probably linear for these times of storage? 



39. Would the above data cause you to accept, or to reject, the hypothesis 

 that the riboflavin concentration in raw pork loin is increased by 12 weeks of 

 storage at, or below, 10°F? 



40. Can the apparent drop in riboflavin concentration between the fortieth 

 and the fifty-sixth weeks of storage reasonably be assigned to sampling acci- 

 dents? Ans. G = 0.202, n = 9, P > .10; accept # (m 4 o = M 56 )- 



41. Use the £ -distribution to set a 95 per cent confidence interval on the true 

 riboflavin concentration in raw, unstored, pork loin of the kind sampled here. 

 You are given that SX = 21.05, and SX 2 = 52.3121. 



42. Solve problem 41 by means of the G-distribution, and compare the result 

 with that obtained from the £ -distribution. 



Ans. From G: 1.9=^ — 2.8; from t: 1.8==> — 2.9. 



