Re: Curious about K-S test in NPTESTS

Posted by Beckstead, Jason on Dec 09, 2018; 6:14pm
URL: http://spssx-discussion.165.s1.nabble.com/Curious-about-K-S-test-in-NPTESTS-tp5737122p5737125.html

Thanks to all. You guys confirmed my hunch. I guess that the best way to compare the difference between two or more distributions of 5 values (like those resulting from different sets of verbal anchors on Likert-type scales) is to use chi-square test.

Jason

sent via me phone

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From: Rich Ulrich <[hidden email]>
Sent: Saturday, December 8, 2018 8:19:14 PM
To: [hidden email]; Beckstead, Jason
Subject: Re: Curious about K-S test in NPTESTS

 

Your apparent difference is not location (mean), but "scale"

(standard deviation). Since the K-S test is sensitive to both, it

will not be especially powerful for either. 

A second generic problem is that rank-based tests, in derivation

and in most casual discussion, assume that there are no ties -- but

your data features only 5 values for 200 cases. Many ties. Sometimes

having ties is mainly notable for making the test-values wrong (so,

Jon's use of "exact stats" for p-level is good practice); sometimes,

like here, it also is reflected in a weakened test.

I put the 10 cells in a 2x5 contingency table, ignoring order, and the

online calculator gave me X2= 18.83, p< .001 (4 d.f.), which looks okay.

--

Rich Ulrich

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From: SPSSX(r) Discussion <[hidden email]> on behalf of Beckstead, Jason <[hidden email]>
Sent: Saturday, December 8, 2018 4:21 PM
To: [hidden email]
Subject: Curious about K-S test in NPTESTS

 

Hi all,

I am working to compare various sample distributions and thought that the Kolmogorov-Smirnov test in NPTESTS would be appropriate. However, it doesn’t reveal these two obviously different distributions as significant. Syntax is below. Any insight would be appreciated.

Jason

 

DATA LIST FREE/FORM X FREQ.

BEGIN DATA.

1 1  7

1 2 24

1 3 38

1 4 24

1 5  7

2 1 20

2 2 20

2 3 20

2 4 20

2 5 20

END DATA.

WEIGHT BY FREQ.

VARIABLE LEVEL X (SCALE).

*Nonparametric Tests: Independent Samples.

NPTESTS

  /INDEPENDENT TEST (X) GROUP (FORM) KOLMOGOROV_SMIRNOV

  /MISSING SCOPE=ANALYSIS USERMISSING=EXCLUDE

  /CRITERIA ALPHA=0.05  CILEVEL=95.

 

_____________________________________________________________

 Jason W. Beckstead, Ph.D.       

  Associate Professor/Quantitative Methodologist

  University of South Florida College of Public Health

  13201 Bruce B. Downs Blvd., MDC56, Tampa, FL 33612, USA

  Statistical Editor, International Journal of Nursing Studies

  phone: [phone]  fax: [phone]          

  personal website:  http://personal.health.usf.edu/jbeckste/

  International Journal of Nursing Studies  http://www.elsevier.com/ijns

 

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===================== To manage your subscription to SPSSX-L, send a message to [hidden email] (not to SPSSX-L), with no body text except the command. To leave the list, send the command SIGNOFF SPSSX-L For a list of commands to manage subscriptions, send the command INFO REFCARD