Statistical and practical significance
Download
1 / 24

Statistical and Practical Significance - PowerPoint PPT Presentation


  • 164 Views
  • Uploaded on
  • Presentation posted in: General

Statistical and Practical Significance. Advanced Statistics Petr Soukup. Outline. Reminder of statistical significance Limits of statistical significance Misuses of statistical significance Alternatives to statistical significance Practical significance Effect sizes.

loader
I am the owner, or an agent authorized to act on behalf of the owner, of the copyrighted work described.
capcha

Download Presentation

Statistical and Practical Significance

An Image/Link below is provided (as is) to download presentation

Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author.While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server.


- - - - - - - - - - - - - - - - - - - - - - - - - - E N D - - - - - - - - - - - - - - - - - - - - - - - - - -

Presentation Transcript


Statistical and Practical Significance

Advanced Statistics

Petr Soukup


Outline

  • Reminder of statistical significance

  • Limits of statistical significance

  • Misuses of statistical significance

  • Alternatives to statistical significance

  • Practical significance

  • Effect sizes


REMINDER OF STATISTICAL SIGNIFICANCE (NHST)


Hypotheses and tests

  • Tested hypothesis in experiments (Fisher, 1925)

  • Null and alternative hypothesis (NHST) (Neyman&Pearson, 1937)

  • Common tests - t-tests, analysis of variance, analysis of covariance, correlation analysis etc.


Definition of statistical significance

Definition: Conditionalprobability, that our sample can

be drawn from population in which null hypothesis

is valid (α). Statistical significance is P(D/H0) and not P(H0/D)


LIMITSOF NHST


Assumptions for classical NHST

  • Big big probability samples from infinite or very big finite populations

    Three assumptions:

  • Big (infinite) population (at least 100times bigger than the sample)

  • Probability sampling (all units same probability of selection)

  • Big sample (> 30-50 units)


LIMITS OF NHST

  • 1.data from censuses

  • 2. data from non-probability samples

  • 3. data from small samples

  • 4. data based on sample that are big proportion of the basic population

  • 5. big data samples from merged (internationally or by time) files


Beyond the limits of NHST in CSR*

N=32 articles, Czech sociological review 2000-2006 (selected 29 issues), own research

*CSR-Czech sociological review


MISUSES OF NHST


Objections against NHST (Misuses of NHST)

a) Insufficient statement about population,

b) null hypotheses are unreal (nill null),

c) mechanical usage of classical 5% statistical significance (asterisks, stepwise methods, best models etc.),

d) statistical significant doesn’t mean important,

e) publishing only statistical significant results (file drawer problem).


Misuses of NHST in CSR*

N=32 articles, Czech sociological review 2000-2006 (selected 29 issues), own research

*CSR-Czech sociological review


Conference examples (P<0,01)


Conference examples (***)


Conference examples (*** and stepwise)


ALTERNATIVESTO NHST


Some alternatives to statistical significance

a) Confidence Intervals (Problems for r, formulas, regression etc.)

b) Test power (quite good in sociology),

c) Estimate of minimum sample size & What if strategy,

d) Comparison of models via information criterias (AIC, BIC)

e) Bayesian approach


PRACTICAL SIGNIFICANCE


Practical significance - terminology

  • Practical significance

    b) Substantive significance

    c) Logical significance

    d) Scientific significance

    sometimes also:

    e) result importance or

    f) result meaningfulness


How to measure Practical sig.?

History - Absolute and relative approach

Example: Income differencies

Absolute and relative difference


How to measure Practical sig.?

Effect sizes – measures of practical significance

Some well known:

Cohen d

Hayes ω

But also R2, r, C, Fisher η2 are effect sizes

Problem: Sometimes published but not interpreted


OTHER SIGNIFICANCES


Special significances

  • Economic significance

  • Clinical significance

  • Etc.


CONCLUSION?

Statistical significance is:

LIMITED

MISUSED

BUT NOT BAD

Substantive significance is:

NOT OFTEN USED

BUT NECESSARY


ad
  • Login