Dear,
I was looking into the hip breadth of the Dutch adults mixed 2004 (age 20-30) and the Dutch students 2016 (age 17-27). In the adult dataset, 390mm corresponds with P42. While in the student dataset it corresponds with P75. This seems to be quite a difference. Is the data collected using the same method? Or what could explain this difference (as the ages are almost the same)?
Kind regards,
Marinke Callens
Dear Marinke
It seems strange, I agree although these differences make sense. Maybe the most important reason is the different sample had different numbers male and female. Ideal would be to measure each time homogenous 100male and 100 female. Because I was leading these investigations I can give the following answer.
We measured 50 variables on 354 students in 1986 and 40 variables of about 400 students in 2014. About the differences we wrote a paper. You can find it on [30 years difference]((PDF) Thirty years of anthropometric changes relevant to the width and depth of transportation seating spaces, present and future (researchgate.net)) . The DINED2004 sample is in fact measured in 1998 as a part of the Geron Project in which we measured 600 healthy elderly and 150 young adults to compare the age effect on all the 79 measured variables. Only 40 where anthropometric. The full report can be found on Design relevant characteristics of ageing users . All 3 samples give an impression of the distribution of the hipwidth sitting. But the differences can be caused by age because people get heavier between age 25-35 on the average for example by pregnancy, by more or less people from other countries: people from Asia are mostly smaller;) Further a sample outcome is not the truth it still is a sample that gives an impression of the population. The mean and standard deviation in mm of the 3 samples are: 372(27) in 1986; 350(23) in 2014 and 396(29) in 1998 in the young adults but only a few students. Higher education mostly causes higher stature and less weight including also less hipwidth. So concluded: each sample will differ even if taken from the same population. If the sample would be measured more frequently and more standardized the results would be beter . So in the future I expect we will measure more and more with 3D scanners which means with less influence by the measurer and we will get more accurate estimation of the population values. It all depends on the available budget because for each dimension on DINED we have to find about 10 euro per person. This means for a sample of 1000 people and 100 body dimensions I would estimate we need a budget of 1 million Euro. That is the main reason why we don’t measure as frequent as we would like to monitor the changes in peoples body shape and dimension because of secular changes (that have stopped in NL) but more because of growing obesity (that is still a growing concern). Hope this gives some explanation about the differences you found.
In addition: the results of the sample measurements could be modified a little by recalculating the mean and sd for each gender and an equal number of people for example 100 female and 100 male. This is however not always useful. I have used sometime 70% female +30% male for a recommendation for a nursing home because that is the gender distribution in a nursing home.
Thereafter you can do the same for age and ethnicity to fit your sample data more into the context of your target design context.
That is a clear answer, thank you, also for the tips.