Notices
Results 1 to 9 of 9

Thread: Which statistical test for comparing two rates?

  1. #1 Which statistical test for comparing two rates? 
    New Member
    Join Date
    Feb 2012
    Posts
    4
    I have data for the rate of photosynthesis for two species for my biology A level coursework, I am required to do a statistical test to show significance but I'm unsure of a test for comparing two rates. Any advice would be appreciated, thanks.


    Reply With Quote  
     

  2.  
     

  3. #2  
    Forum Freshman
    Join Date
    Feb 2012
    Location
    Amsterdam
    Posts
    7
    Do you mean two rates as in two average numbers, one for each species? The type of test you can use may depent on some particular properties of your data. For example, are variances equal and is your 'rate of photosynthesis' normally distributed? If this is the case, I think an 'independent t-test' as well as an 'ANOVA' will work. Both compare two mean values, but since ANOVA is mostly used when multiple t-tests are required I think an independent t-test will do the job. Think you can work with this?


    Reply With Quote  
     

  4. #3  
    New Member
    Join Date
    Feb 2012
    Posts
    4
    Quote Originally Posted by seignet View Post
    Do you mean two rates as in two average numbers, one for each species? The type of test you can use may depent on some particular properties of your data. For example, are variances equal and is your 'rate of photosynthesis' normally distributed? If this is the case, I think an 'independent t-test' as well as an 'ANOVA' will work. Both compare two mean values, but since ANOVA is mostly used when multiple t-tests are required I think an independent t-test will do the job. Think you can work with this?
    The data I have for each species is for a rate as in an accumulated value of total oxygen output for every 1 minute up to ten minutes.
    Reply With Quote  
     

  5. #4  
    Forum Bachelors Degree
    Join Date
    Jul 2008
    Posts
    420
    Hi jblox,

    First calculate the rate of photosynthesis for each species, using your raw data on Oxygen output, then perform an unpaired t-test to see if there is a significant difference in photosynthesis rate between the two species.

    http://www.marietta.edu/~spilatrs/biol103/photolab/photosyn.html

    http://en.wikipedia.org/wiki/T_test


    B
    est wishes,

    Tridimity

    P.S. I think this is correct, but please check with someone else before you take my word for it, since it's actually quite important that you get this right!
    Reply With Quote  
     

  6. #5  
    Forum Freshman
    Join Date
    Feb 2012
    Location
    Amsterdam
    Posts
    7
    Do you mean like this?

    species A: V1; V2; V3; V4; V5; V6; V7; V8; V9; V10
    species B: V1; V2; V3; V4; V5; V6; V7; V8; V9; V10

    What exactly do you want to know? The difference between each V-pair (V1A compared to V1B, V2A compared to V2B etc.)? Or the difference between oxygen output/minute in A compared to oxygen output/minute in B? For the latter, you can simply calculate both rates (devide V10 by ten) and use an independent t-test to compare.
    Reply With Quote  
     

  7. #6  
    New Member
    Join Date
    Feb 2012
    Posts
    4
    Quote Originally Posted by seignet View Post
    Do you mean like this?

    species A: V1; V2; V3; V4; V5; V6; V7; V8; V9; V10
    species B: V1; V2; V3; V4; V5; V6; V7; V8; V9; V10

    What exactly do you want to know? The difference between each V-pair (V1A compared to V1B, V2A compared to V2B etc.)? Or the difference between oxygen output/minute in A compared to oxygen output/minute in B? For the latter, you can simply calculate both rates (devide V10 by ten) and use an independent t-test to compare.
    Ok, so I have my rates, but what formulas do I need to use? I can seem to find any usefull T-test tutorials.
    Reply With Quote  
     

  8. #7  
    Forum Bachelors Degree
    Join Date
    Jul 2008
    Posts
    420
    Yes, it would be most informative to compare the overall photosynthesis reaction rates between the two species, rather than trying to compare the individual Oxygen outputs at each time point.

    This Wikipedia link provides some information on how to perform an independent (unpaired) t-test - see section 5.3: Student's t-test - Wikipedia, the free encyclopedia

    Scroll down to section 6 for worked examples.

    Best wishes,

    Tridimity
    Reply With Quote  
     

  9. #8  
    Forum Bachelors Degree
    Join Date
    Jul 2008
    Posts
    420
    Oh, and if you have access to SPSS, you can enter your data and perform an unpaired t-test via Analyse > Compare Means > Independent Samples t-test
    Reply With Quote  
     

  10. #9  
    New Member
    Join Date
    Feb 2012
    Posts
    4
    I have sorted it now. Thanks to everyone that helped out.
    Reply With Quote  
     

Similar Threads

  1. Comparing science across cultures?
    By miwashi in forum General Discussion
    Replies: 0
    Last Post: August 7th, 2011, 10:06 PM
  2. Comparing (unlabelled) nested sets
    By worldsayshi in forum Computer Science
    Replies: 2
    Last Post: April 9th, 2011, 09:59 AM
  3. rates of change
    By Heinsbergrelatz in forum Mathematics
    Replies: 5
    Last Post: July 27th, 2010, 09:24 PM
  4. Comparing: Tired Light vs. Dark Matter/Energy
    By kojax in forum Astronomy & Cosmology
    Replies: 3
    Last Post: October 1st, 2008, 07:04 PM
  5. Why is the Turing Test considered a good test of AI?
    By angrysoba in forum Computer Science
    Replies: 1
    Last Post: October 17th, 2006, 11:38 AM
Bookmarks
Bookmarks
Posting Permissions
  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •