Page 69 - Anthropometry, Apparel Sizing and Design
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98 Anthropometry, Apparel Sizing and Design
where
N¼ total number of target population.
X i ¼ input for sample i.
Y i ¼ output for sample i
x¼ mean value of input data
y¼ mean value of output data
The body dimensions used to calculate the sample size are the common key dimen-
sions for a sizing system: height, chest girth, bust girth, waist girth, and hip girth. After
figuring the total sample size, the sample size for each of the strata can be calculated
using Eq. (1.2), and then the total number of subjects for each age range and gender
can be calculated based on the proportionate method formula (Eq. 1.3).
First step:
1
y ¼ ½ N 1 y + N 2 y + … + N l y (1.2)
st
l
2
1
N
where
N¼ total population age 7–17
N 1 ¼ total population age 7–12
N 2 ¼ total population age 13–17
y 5 mean of variables for each age group
Second step:
2
0:01 y st
D ¼ (1.3)
2:326
Third step:
Calculating the sample size using stratified random sampling (Eq. 1.1)
To calculate the sample size, the age range for the sample population is calculated,
and then the total population in the geographical area is calculated. For example, the
total population in one state is 823,071[N]. The number of subjects in each age group
is then tabulated. Each age group forms a stratum, and the sample for each stratum is
calculated using the proportionate method according to the ratio of the real population.
Each stratum age [h] is given by
n h¼ N h =Nð Þ ∗ n (1.4)
where n h is the sample size for stratum h, N h is the population size for stratum h, N is
total population size, and n is the sample size.
For example, the male-to-female ratio in the real population in one state is 51%
male and 49% female. For each age range the sample is divided into the corresponding
ratio (n) of male and female:
n m ¼ N h∗ n (1.5)
