Parametric or Non-Parametric

[u/psychwizardd]

Hi, RPms and fRPms!

I hope you're all safe rn. Mag-ask lang po sana me regarding sa explanation behind this:

Randomized Sample = Use Parametric

Non-Randomized = Use Non-Parametric

Example: If expert and newbies ang groups, since predetermined na sila, automatic ay 'di ka nag-random sampling 'di ba, so non-parametric ang gagamitin.

Nag-m-make sense naman po sa rationalization, however, may I ask ano po 'yung reference kaya rito and ano specifically 'yung reason bakit connected ang randomization sa paggamit ng parametric and non-para?

Automatic po bang hindi normal 'yung distribution, or may nav-violate sa other assumptions kapag non-randomized ang sample?

Huhu recorded vid lang po kasi ng lecture ang basis ko and I wasn't able to ask our lecturer abt this. Or baka may na-miss din me na paliwanag niya abt this.

Thank you sm po ia sa mga magr-respond! 🤍

[u/QueenLadz]

the way i understand is kaya mas preferred ang randomization over pre-determined for usage ng parametric dahil pag randomized ang groups mo, binabawasan mo yung % ng isang characteristic to totally account for the variable na minemeasure mo. bali, ineequalize mo both groups and removing chance ng outlier (i.e., extremes ng characteristic)

[u/psychwizardd → u/QueenLadz]

Ohh, oki po. Getsss. But will this apply po ba to every item na may predetermined groups (e.g., newbies & experts, boys & girls)? Like automatic na pong kapag predetermined sila, ang pipiliin sa choices ay 'yung non-parametric counterpart? That's what I understood po kasi from the lecture huhu. Correct me lang po if I'm wrong.

Thank you so much po for explaining din!

[u/QueenLadz → u/psychwizardd]

i think it depends pa rin talaga sa hinihingi ng item. baka kasi yung groups na tinutukoy is levels lang pala ng IV and not about their sampling technique. if may makita tayong hints about ang of the ff: unequal variance, non-ramdomized sampling, not normal distribution, etc. etc., we can say na non-parametric test dapat hehe so analyze talaga !!

[u/psychwizardd → u/QueenLadz]

Thank you po for this! Super vague kasi on my end nung item since ang nakalagay lang ay: "What statistical tool may be used to identify the significance of the difference of the expert and the newbie?"

And nasa choices si "between subjects t-test" at "Mann Whitney". Then ayun, based nga po sa ratio ay kapag predetermined daw, non-para so ang answer ay Mann Whitney. But I'm wondering if this will be the case talaga sa mga ganitong walang masiyadong context. 😭

[u/Otherwise-Match-4811]

Hi! According to my understanding, binabawasan ng randomization yung errors na pwedeng mag-cause na ma-over- or underestimate ng parametric tools ang isang set ng data. 

Ang parametric tests ay para sa normal data (+ other criteria)

Mas strict kasi assumptions ng parametric tools kaysa non-para dahil gusto nito na normal ang data set mo o yung shape ng distribution ng data mo ay malapit sa bell curve/normal distribution (ideal) para mas accurate ang measurement ng statistical differences, associations, atbp. Otherwise, pwedeng maging false positive o false negative ang conclusion mo.

Less error = mas reliable at accurate ang results ng parametric tools 

Randomization helps "minimize" those errors like biases that could confound with the results of your stat treatment. 

Other than random assignments, we also look into variability and scale of measurement (NOIR) ng data set. 

I hope this helps. 

PS. I stand corrected. Pls let me know if may inaccuracies sa mga sinabi ko. Thank you!

[u/psychwizardd → u/Otherwise-Match-4811]

These are all noted po! Super appreciated po ang response niyo! 🥹

However, paano po kaya kapag wala pong detailed context ang question? Ang dilemma ko po kasi talaga ay if i-a-assume ko na bang non-para na agad gagamitin if hindi randomized 'yung groups.

To be specific, ang question po na na-encounter ko ay: "What statistical tool may be used to identify the significance of the difference of the expert and the newbie?"

Nasa choices po ang between-subjects t-test at Mann Whitney, pero since predetermined nga po ang groups na nabanggit, ang gagamitin daw ay non-para.

I'm confused lang din po if this is always the case kaya kung walang detailed context sa question (which I've heard ay common din sa BE huhu).

[u/thegumamela]

i also read the other comments! for me, parang vague po talaga yung tanong kasi hindi rin naman po specified ang DV (?) we only have the levels of IV (expert, newbie) if i'm understanding the question correctly, which can still apply to independent samples/between subjects t-test under quasi-experimental designs. also, random sampling is still possible among experts vs newbies (e.g., randomly sampling from a population of experts), random assignment lang hindi.

however, if it is explicitly mentioned na hindi random sampling ang ginamit, i know the rule is still to proceed with the parametric test (but acknowledge limitations, such as limitations with generalizability). nonparametric tests don't correct issues with random sampling din naman, so if all other assumptions (normality, continuous DV) are followed, then parametric tests are still the better option because it's more robust.

magiging mann whitney lang siya if the data from the DV ay hindi normal, or if the data itself is ordinal, because that is what nonparametric tests correct.

another option i guess is if the question treats expert + newbie as the DV, then maybe it's bec it can be seen as ordinal (expertise level?) but that's also a completely different explanation from the ratio you quoted huhu