The distribution of body weight for young girls age 0-3 years can be used to evaluate the physical development of a child.
Data: body weight in kilograms
|
month |
5th% |
10th% |
25th% |
50th% |
75th% |
90th% |
95th% |
|---|---|---|---|---|---|---|---|
|
0 |
2.36 |
2.58 |
2.93 |
3.23 |
3.52 |
3.64 |
3.81 |
|
1 |
2.97 |
3.22 |
3.59 |
3.98 |
4.36 |
4.65 |
4.92 |
|
3 |
4.18 |
4.47 |
4.88 |
5.4 |
5.9 |
6.39 |
6.74 |
|
6 |
5.79 |
6.12 |
6.6 |
7.21 |
7.83 |
8.38 |
8.73 |
|
9 |
7 |
7.34 |
7.89 |
8.56 |
9.24 |
9.83 |
10.17 |
|
12 |
7.84 |
8.19 |
8.81 |
9.53 |
10.23 |
10.87 |
11.24 |
|
18 |
8.92 |
9.3 |
10.04 |
10.82 |
11.55 |
12.3 |
12.76 |
|
24 |
9.87 |
10.26 |
11.1 |
11.9 |
12.74 |
13.57 |
14.08 |
|
30 |
10.78 |
11.21 |
12.11 |
12.93 |
13.93 |
14.81 |
15.35 |
|
36 |
11.6 |
12.07 |
12.99 |
13.93 |
15.03 |
15.97 |
16.54 |
Polynomial equations approximating this data were calculated in JMP, as follows:
5th% for body weight in kilograms =
= ((-0.000007 * ((months)^4)) + (0.0008141 * ((months)^3)) - (0.033894 * ((months)^2)) + (0.7610993 * (months)) + 2.2805025)
10th% for body weight in kilograms =
= ((-0.000008 * ((months)^4)) + (0.0008763 * ((months)^3)) - (0.035785 * ((months)^2)) + (0.7871032 * (months)) + 2.5045076)
25th% for body weight in kilograms =
= ((-0.000008 * ((months)^4)) + (0.0008543 * ((months)^3)) - (0.035339 * ((months)^2)) + (0.8069777 * (months)) + 2.8537413)
50th% for body weight in kilograms =
= ((-0.000008 * ((months)^4)) + (0.000942 * ((months)^3)) - (0.039113 * ((months)^2)) + (0.8750996 * (months)) + 3.1727893)
75th% for body weight in kilograms =
= ((-0.000012 * ((months)^4)) + (0.0012394 * ((months)^3)) - (0.047108 * ((months)^2)) + (0.9683973 * (months)) + 3.4630431)
90th% for body weight in kilograms =
= ((-0.000015 * ((months)^4)) + (0.0015248 * ((months)^3)) - (0.055114 * ((months)^2)) + (1.0707593 * (months)) + 3.6361131)
95th% for body weight in kilograms =
= ((-0.000017 * ((months)^4)) + (0.0016508 * ((months)^3)) - (0.058214 * ((months)^2)) + (1.1077472 * (months)) + 3.8491879)
Distribution of Weight by Month
If the same data is analyzed for each month, then the percentile represented by a given weight can be derived. Initially third and fourth order polynomial equations were tried, but were found to be inaccurate. Using 2 second order polynomials for above and below the 50th percentile gave equations adequate for most clinical situations.
0 to 3 years, 5 to 50%ile
|
Age in years |
wgt^2 |
wgt |
constant |
|---|---|---|---|
|
0 |
51.4975130 |
-236.81980 |
277.43047 |
|
0.08 |
31.7763770 |
-176.23790 |
248.09476 |
|
0.25 |
17.3920040 |
-129.32670 |
241.35898 |
|
0.5 |
12.4423640 |
-129.72300 |
338.63512 |
|
0.75 |
10.0010610 |
-126.56140 |
400.63952 |
|
1 |
8.5316185 |
-121.47250 |
432.82506 |
|
1.5 |
7.3561926 |
-121.59500 |
504.41654 |
|
2 |
7.0404320 |
-131.32900 |
615.69639 |
|
2.5 |
6.7795130 |
-140.07040 |
727.51743 |
|
3 |
5.1141372 |
-111.33930 |
608.52826 |
0 to 3 years, 51 to 95%ile
|
Age in years |
wgt^2 |
wgt |
constant |
|---|---|---|---|
|
0 |
-59.976060 |
502.25993 |
-946.9905 |
|
0.08 |
-36.374870 |
372.31023 |
-855.846 |
|
0.25 |
-19.526170 |
270.62484 |
-841.9886 |
|
0.5 |
-12.228280 |
224.64363 |
-934.0595 |
|
0.75 |
-9.691979 |
209.58069 |
-1033.888 |
|
1 |
-9.365721 |
220.86997 |
-1204.301 |
|
1.5 |
-8.886865 |
232.64042 |
-1426.692 |
|
2 |
-6.713345 |
195.00787 |
-1319.883 |
|
2.5 |
-4.625871 |
149.48733 |
-1109.546 |
|
3 |
-3.757316 |
131.81509 |
-1057.16 |
