Turn on thread page Beta
    • Thread Starter
    Offline

    12
    ReputationRep:
    Considering the following table:

    Name:  Capture.JPG
Views: 51
Size:  23.2 KB

    Across the top are different discussion topics, and vertically are political parties. The numbers in the cells represent the number of times that party speaks on that topic.

    I want to find out if there is a statistically significant difference on what each party focusses on or whether all parties discuss the same topics equally.

    I would use a chi-squared test, but I'm doing the same for 4 other tables. A couple of these tables have an expected value less than 5 (see lib dems) hence breaking one assumption, see below:



    Which test would be applicable to all of my tables when testing for statistic significance and whether the parties vary by topic?

    Many thanks
    Attached Images
      
    • Thread Starter
    Offline

    12
    ReputationRep:
    Anyone?
    Offline

    14
    ReputationRep:
    (Original post by Jamie S)
    Anyone?
    Sorry, I managed to miss this post yesterday! The usual advice that you will see is that the Chi-squared test is unreliable if expected cell sizes occur with values less than five. (I believe this is still widely taught at school) and one is often directed to the Fisher exact test in these cases. The actual situation is more complicated than that, and the chi-squared test is often much more resilient than that simple rule suggests.

    In real life, we tend to use chi-squared tests where the p-values are worked out by monte-carlo simulation from the set of all tables with the same row and column sums as the table under consideration.

    So, first question: is this for a school or university assignment? If so, we may have to be a bit more sensitive to the out of data advice alluded to above!

    If this is "real" work, then we can apply a vanilla chi-squared test, a monte-carlo chi-squared test, and a Fisher exact test. If you do that with the table you have given, the p-values all come out at about 0.08-0.09 - in other words the different ways of doing it are all saying the same thing: no evidence to reject the null hypothesis on no association between rows and columns.

    BTW, I'm not sure I what you mean by observing that "but I'm doing the same for 4 other tables". Are you asking about whether a correction for multiple testing should be done?
    • Thread Starter
    Offline

    12
    ReputationRep:
    (Original post by Gregorius)
    Sorry, I managed to miss this post yesterday! The usual advice that you will see is that the Chi-squared test is unreliable if expected cell sizes occur with values less than five. (I believe this is still widely taught at school) and one is often directed to the Fisher exact test in these cases. The actual situation is more complicated than that, and the chi-squared test is often much more resilient than that simple rule suggests.

    In real life, we tend to use chi-squared tests where the p-values are worked out by monte-carlo simulation from the set of all tables with the same row and column sums as the table under consideration.

    So, first question: is this for a school or university assignment? If so, we may have to be a bit more sensitive to the out of data advice alluded to above!

    If this is "real" work, then we can apply a vanilla chi-squared test, a monte-carlo chi-squared test, and a Fisher exact test. If you do that with the table you have given, the p-values all come out at about 0.08-0.09 - in other words the different ways of doing it are all saying the same thing: no evidence to reject the null hypothesis on no association between rows and columns.

    BTW, I'm not sure I what you mean by observing that "but I'm doing the same for 4 other tables". Are you asking about whether a correction for multiple testing should be done?
    I'm a research assistant for a Professor of Political Science at the LSE. This result (depending on how interesting the findings are) will be used firstly as an appendix to an Academic Book, and secondly may be published independently in a number of Political Science Journals.

    I am a political scientist by training, not a statistician so would not know very well how to do more complex tests - hence would be thankful if you could advise, teach or explain those to me. Although I do have access to 1) Stata 2) SPSS and 3) the internet tutorials. If worse comes to worse I can always contact the Stats department.

    As for more details on the study, I would prefer to message you directly.
    Offline

    14
    ReputationRep:
    (Original post by Jamie S)
    I'm a research assistant for a Professor of Political Science at the LSE. This result (depending on how interesting the findings are) will be used firstly as an appendix to an Academic Book, and secondly may be published independently in a number of Political Science Journals.

    I am a political scientist by training, not a statistician so would not know very well how to do more complex tests - hence would be thankful if you could advise, teach or explain those to me. Although I do have access to 1) Stata 2) SPSS and 3) the internet tutorials. If worse comes to worse I can always contact the Stats department.

    As for more details on the study, I would prefer to message you directly.
    I'm happy to give you some advice on here, but it strikes me that if this work is important and with high visibility, it might be a good idea to have a chat with a local statistician. You may not need to go to the Stats department, though - I would have thought that LSE Political Science would have a few people adept at this sort of quantitative analysis hanging around!
 
 
 
Reply
Submit reply
Turn on thread page Beta
Updated: June 12, 2016

1,000

students online now

800,000+

Exam discussions

Find your exam discussion here

Poll
Should predicted grades be removed from the uni application process
Useful resources

Make your revision easier

Maths

Maths Forum posting guidelines

Not sure where to post? Read the updated guidelines here

Equations

How to use LaTex

Writing equations the easy way

Student revising

Study habits of A* students

Top tips from students who have already aced their exams

Study Planner

Create your own Study Planner

Never miss a deadline again

Polling station sign

Thinking about a maths degree?

Chat with other maths applicants

Can you help? Study help unanswered threads

Groups associated with this forum:

View associated groups

The Student Room, Get Revising and Marked by Teachers are trading names of The Student Room Group Ltd.

Register Number: 04666380 (England and Wales), VAT No. 806 8067 22 Registered Office: International House, Queens Road, Brighton, BN1 3XE

Write a reply...
Reply
Hide
Reputation gems: You get these gems as you gain rep from other members for making good contributions and giving helpful advice.