72 
Journal of Agricultural Research 
Vol. XIV, No. 2 
hoestein-friesian 
Tables XI to XIV exhibit the distributions of individuals with regard 
to the yield of milk and the percentage of fat in the form of correlation 
tables. Table XV combines Tables XI to XIV. Table T> summarizes 
the means, standard deviations, coefficients of variability for milk and 
fat, and the correlations between percentage of fat and yield for Hol- 
stein-Friesians of different ages. 
Table D. —Summary of results from a study of the correlation between the percentage of 
fat and yield of milk for Holstein-Friesians 
[Fat in percentage; milk in pounds] 
Age. 
Num¬ 
ber of 
ani¬ 
mals. 
Years. 
2 to 3. 
610 
3 to 4. 
341 
4 to 5 . 
292 
5 and over.... 
682 
All ages. 
1,925 
Type of 
test. 
Mean 
Standard 
deviation. 
Coefficient 
of 
variability. 
Correlation. 
/Milk 
\Fat. 
/Milk 
\Fat. 
/Milk 
\Fat. 
/Milk 
\Fat. 
/Milk 
\Fat. 
12,488.5 ±80.4 
3.462+ 0.008 
*3,938-5 ±116.5 
3.433 ± 0.012 
14,825*5 ± 134-4 
3.4i7± 0.012 
16,280.0 ±94.4 
3.420± o. 008 
14,443.1 ± 56. o 
3 - 435 ± 0-005 
2,942. o ± 56. 8 
o. 294 ± o. 006 
3,188.0 ±82.4 
O. 322± 0.008 
3,151-0 ±87*9 
o. 3*3± 0.009 
3 , 654-5 ±66.7 
o. 301 ± 0.006 
3,640.7 ±39.6 
o. 305 ± 0.003 
23.56+0.48 
8. 50+0. 16 
22. 87+0. 62 
9. 38±o. 24 
21. 25±o. 62 
9. i7±o. 26 
22.45±o* 43 
8. 81 ±0.16 
25. 21 ±0. 29 
8.88+o. 10 
—c. 116+0.027 
—o. 160+0. 039 
—o. o88± 0.039 
J—0:115 ±0.026 
f—o. i33±o. oi5 
The correlations are much smaller for the Holstein-Friesian than for 
the two preceding breeds. They range from —0.088 ±0.039 to — 0.160 ± 
0.036. The first is not significant when judged by the probable error. 
The milk yields increase regularly from 12,488 pounds for the youngest 
class to 16,280 for the oldest. The percentages of fat remain practically 
constant for the different ages. (See fig. 2.) 
AYRSHIRE 
Tables XVI to XIX are correlation tables for the different classes of 
Ayrshires. Table E gives means, standards deviations, coefficients of 
variability for milk and fat, and the correlations between percentages of 
fat and yield of milk. 
Table E. —Summary of results from a study of the correlation between the percentage of 
fat and yield of milk for Ayrshires 
[Fat in percentage; milk in pounds] 
Age. 
>• 
Num¬ 
ber of 
ani¬ 
mals. 
Type of 
test. 
Mean. 
Standard devia¬ 
tion. 
Coefficient of 
variability. 
Correlation. 
Years. 
2 to 3 ... 
3 to 4... 
4 to 5. 
5 and over. 
All ages. 
343 
192 
160 
396 
1,091 
/Milk. 
\Fat. 
/Milk. 
\Fat....... 
/Milk. 
\Fat. 
/Milk. 
\Fat. 
/Milk. 
\Fat. 
7,960.5 ± 47-9 
4.016+ 0. on 
9,179-5 ±86.1 
3 - 936 ± 0.014 
9,584-5 ±83.5 
3-9l9± 0.016 
10,726.0 ±67.1 
3.865 + 0. on 
9 , 417-1 ± 4 i -7 
3-933± 0.006 
1,314-5 ± 33-9 
o-3io± 0.008 
1.769.5 ±60.9 
0.3i4± 0. on 
1.566.5 ±59.1 
0.303 ± O.OII 
1,980.0 ±47-5 
0.3i3± 0.008 
2,044.4 ±29.5 
0.3i8± 0.005 
* 
16. 5 i±o -44 
7. 7i±o. 20 
19. 28 ±o. 69 
6. 35±o. 28 
16. 34 ±o- 63 
7 - 73 ± 0 - 29 
18. 46±o. 46 
8- io±o. 19 
21. 7 i±o -33 
8.o8±o. 12 
l+o. 019+0.036 
0.093 ±0.048 
0.023+0.053 
j—0.047+0.034 
0.138+0.020 
