V Excelu imam seznam podatkov, ki jim poskušam določiti kvartile. Težavo imam pri vrednostih prvega in tretjega kvartila.
Za 1. kvartil (to je mediana 1. polovice podatkov) sem uporabila funkcijo =QUARTILE(podatki;1). Funkcija vrne 48,625, jaz pa sem izračunala 46,5.
Za 2. kvartil, sem uporabila isto funkcijo, tu dobim pravi rezultat, to je 58,5.
Za 3. kvartil uporabim funkcijo =QUARTILE(podatki;3), tu dobim rezultat 65,75, izračunala pa sem 67,5.
To so podatki na katerih določam kvartile: 34,5 42,5 42,5 43 50,5 52,5 55 57 60 62 62 64 71 72 74,5 86,5
Zakaj se pojavijo razlike med računanjem 'peš' in računanjem z Excelom? (izračuni 'peš' so gotovo narejeni pravilno)
Pa še primer računanja kvartilov: http://www.mathsisfun.com/data/quartiles.html (zadnji primer je najbolj podoben mojemu, tudi te podatke sem vnesla v Excel in dobim drugačne razultate)
Kvartili
Re: Kvartili
Pozdravljeni,
glede na to, da ste mi poslali povezavo na angleško stran, sklepam da poznate angleščino in vam podajam kar originalno razlago, brez prevoda (na vprašanje o izračunu za primer števil {4,6,8,12,14,16}):
The short explanation is that Excel is calculating the quartiles as percentiles. This is really quite different from the way we ordinarily think of quartiles (as medians of the upper/lower half of the data). Here's a quick explanation of how Excel does what it does, using your data as an example. I can't be 100% sure this is the exact algorithm Excel uses, but this will give the same results.
This of course is a strange way of calculating a quartile and is not to be found on the Wikipedia page about quartiles.
glede na to, da ste mi poslali povezavo na angleško stran, sklepam da poznate angleščino in vam podajam kar originalno razlago, brez prevoda (na vprašanje o izračunu za primer števil {4,6,8,12,14,16}):
The short explanation is that Excel is calculating the quartiles as percentiles. This is really quite different from the way we ordinarily think of quartiles (as medians of the upper/lower half of the data). Here's a quick explanation of how Excel does what it does, using your data as an example. I can't be 100% sure this is the exact algorithm Excel uses, but this will give the same results.
- Excel assigns PERCENTILES to each value in the array.
Koda: Izberi vse
P(4) = 0; P(6)=0.20; P(8)=0.40; ... ; P(16)=1
- Excel then checks where the requested percentile falls in the array.
Koda: Izberi vse
For Q1, 0.25 falls between 6 and 8.
- Excel then linearly interpolates between these values based on the percentile.
Koda: Izberi vse
0.25 percentile is 0.05 percentile higher than 0.20 percentile. 0.05/(P(8)-P(6)) = 0.05/0.20 = 1/4
This of course is a strange way of calculating a quartile and is not to be found on the Wikipedia page about quartiles.
lp,
Matjaž Prtenjak
Administrator
Matjaž Prtenjak
Administrator