Posted by **Colin** on Thursday, August 13, 2009 at 5:21am.

I have 28 participants. Each completed five tests. The maximum score a participant could receive on any one test was 4/4. The lowest score anyone could receive was zero.

I will do a Friedman test for this paired data.

My question: given that I have a very large number of identical ranks (mostly participants getting zero in all tests) can I still go ahead? I just want to know if there is a significant difference in the medians.

Thanks!

- English -
**bobpursley**, Thursday, August 13, 2009 at 8:34am
Yes, assuming the zero was a valid score, as the person being tested didn't know the subject matter. If the zero is a zero for other reasons (absent, being hardheaded and refusing the test, or similar), then the conclusion on difference is likely to be invalid.

I am reminded of instances were kids put their name on answer sheets, and turn it in as an act of rebellion. You can't make a conclusion about the meaning of scores in that case.

- English -
**Colin**, Thursday, August 13, 2009 at 9:53am
Thanks very much Bob. I much appreciate your taking the trouble to respond.

All the best!

Colin

- English -
**SraJMcGin**, Thursday, August 13, 2009 at 10:02am
After reading Bob's comment, I can't help but remember the best French student I had purposely getting himself a zero but not only putting a wrong answer but the very worst answer! The principal was so angry he wanted to suspend that student but instead I persuaded him to just delete that score, because I knew why he had done that! I'm happy to say that student went on to be a wonderful surgeon.

Sra (aka Mme)

## Answer this Question

## Related Questions

- Friedman test: Can !? - I have 28 participants. Each completed five tests. The ...
- Algebra - Tom took five math tests and got an integer score on each of them. He ...
- math - A teacher allows the students to each "throw out" their lowest test score...
- math - Adam took five tests and received a grade for each of them. The first ...
- math - To get a C in history, Nandan must average 74 on four tests. Scores on ...
- math - A student has a mean score of 88 on five tests taken. What score must she...
- Test and Measures - In a sample of students, the average score on an assessment ...
- Statisitics - In a large section of a Chemistry class, the points for the final ...
- programming concepts - Mr. Jones always gives True/False tests to his class. His...
- programming concepts - Mr. Jones always gives True/False tests to his class. His...

More Related Questions