+ Reply to Thread
Results 1 to 5 of 5

Thread: Comparing two values for significance

  1. #1
    Points: 1,955, Level: 26
    Level completed: 55%, Points required for next Level: 45

    Posts
    5
    Thanks
    0
    Thanked 0 Times in 0 Posts

    Comparing two values for significance




    Looking for a little assistance please. I need to determine whether or not there is a statistical significant difference (p<0.05, with CI of 95%) between two values. I have tried a chi square or t-test but I don't think that works.

    Here we go:

    Total number of patients: 816

    Of the 816 patients, they were broken down into two groups based on blood pressure.

    Group A = 27 patients had a blood pressure of 89 or less
    Group B = 789 patients had a blood pressure of 90 or greater

    Now we looked at the incidence of broken hip bones in these two groups

    In group A, 7/27 or 25.9% had a broken hip
    In group B, 97/789 or 12.3% had a broken hip

    My question is this: is there a significant difference between the incidence of broken bones for group A and group B. ie: Is group A really more likely to have a broken bone. Or, due to my small group A sample size, if the difference not significant.

    Once we figure this out, I have another question as I have broken these groups down even further.

    Thanks to anyone who can help.

    JD

  2. #2
    TS Contributor
    Points: 4,330, Level: 41
    Level completed: 90%, Points required for next Level: 20

    Location
    MD
    Posts
    388
    Thanks
    0
    Thanked 6 Times in 6 Posts
    Hello Rady cardia,
    I think chi square is just great for this.
    Here is a table for your data. Just significant!!
    This message board is addictive.


    Table of bp by hip

    bp hip

    Frequency‚
    Percent ‚broken ‚not ‚ Total
    ƒƒƒƒƒƒƒƒƒˆƒƒƒƒƒƒƒƒˆƒƒƒƒƒƒƒƒˆ
    hi ‚ 97 ‚ 692 ‚ 789
    ‚ 11.89 ‚ 84.80 ‚ 96.69
    ƒƒƒƒƒƒƒƒƒˆƒƒƒƒƒƒƒƒˆƒƒƒƒƒƒƒƒˆ
    lo ‚ 7 ‚ 20 ‚ 27
    ‚ 0.86 ‚ 2.45 ‚ 3.31
    ƒƒƒƒƒƒƒƒƒˆƒƒƒƒƒƒƒƒˆƒƒƒƒƒƒƒƒˆ
    Total 104 712 816
    12.75 87.25 100.00


    Statistics for Table of bp by hip

    Statistic DF Value Prob
    ƒƒƒƒƒƒƒƒƒƒƒƒƒƒƒƒƒƒƒƒƒƒƒƒƒƒƒƒƒƒƒƒƒƒƒƒƒƒƒƒƒƒƒƒƒƒƒƒƒƒƒƒƒƒ
    Chi-Square 1 4.3624 0.0367

  3. #3
    Points: 1,955, Level: 26
    Level completed: 55%, Points required for next Level: 45

    Posts
    5
    Thanks
    0
    Thanked 0 Times in 0 Posts
    Thank you very much for the help.

    Is it possible for you to explain how to do this? I see your chart but it doesn't make sense to my ignorant self.

    I have many more calculations that I need to do for my project and I would like to learn how to do this myself.

    thanks

  4. #4
    R purist
    Points: 20,204, Level: 89
    Level completed: 71%, Points required for next Level: 146
    TheEcologist's Avatar
    Location
    The Netherlands.
    Posts
    1,678
    Thanks
    224
    Thanked 438 Times in 248 Posts
    Quote Originally Posted by radycardia View Post
    Thank you very much for the help.

    Is it possible for you to explain how to do this? I see your chart but it doesn't make sense to my ignorant self.

    I have many more calculations that I need to do for my project and I would like to learn how to do this myself.

    thanks
    Here's a place to start:

    http://udel.edu/~mcdonald/statchiind.html

    And here's a nice selection of more tests:
    http://udel.edu/~mcdonald/statbigchart.html
    The true ideals of great philosophies always seem to get lost somewhere along the road..

  5. #5
    Points: 1,955, Level: 26
    Level completed: 55%, Points required for next Level: 45

    Posts
    5
    Thanks
    0
    Thanked 0 Times in 0 Posts

    Quote Originally Posted by fed1 View Post
    Hello Rady cardia,
    I think chi square is just great for this.
    Here is a table for your data. Just significant!!
    This message board is addictive.


    Table of bp by hip

    bp hip

    Frequency‚
    Percent ‚broken ‚not ‚ Total
    ƒƒƒƒƒƒƒƒƒˆƒƒƒƒƒƒƒƒˆƒƒƒƒƒƒƒƒˆ
    hi ‚ 97 ‚ 692 ‚ 789
    ‚ 11.89 ‚ 84.80 ‚ 96.69
    ƒƒƒƒƒƒƒƒƒˆƒƒƒƒƒƒƒƒˆƒƒƒƒƒƒƒƒˆ
    lo ‚ 7 ‚ 20 ‚ 27
    ‚ 0.86 ‚ 2.45 ‚ 3.31
    ƒƒƒƒƒƒƒƒƒˆƒƒƒƒƒƒƒƒˆƒƒƒƒƒƒƒƒˆ
    Total 104 712 816
    12.75 87.25 100.00


    Statistics for Table of bp by hip

    Statistic DF Value Prob
    ƒƒƒƒƒƒƒƒƒƒƒƒƒƒƒƒƒƒƒƒƒƒƒƒƒƒƒƒƒƒƒƒƒƒƒƒƒƒƒƒƒƒƒƒƒƒƒƒƒƒƒƒƒƒ
    Chi-Square 1 4.3624 0.0367
    Thanks for your help fred, I can follow part of your post, but I don't know where you get some of your numbers.

    I can see the hi = blood pressure above or = to 90. That the first three numbers are the number with a fracture, number without a fracture and the total. But where do you get the next series of three numbers right below that? (I bolded them)

    I can follow the same thing for the low, but where are the second set of three numbers coming from?

+ Reply to Thread

           




Similar Threads

  1. Comparing ind. and dep. significance help!
    By burton160w in forum Statistical Research
    Replies: 5
    Last Post: 12-07-2010, 11:24 PM
  2. Comparing z-values and t-values
    By 3sacharm in forum Statistics
    Replies: 1
    Last Post: 11-15-2010, 12:22 PM
  3. Help on comparing mean to distribution values
    By JoynerCN in forum Probability
    Replies: 7
    Last Post: 06-17-2010, 11:55 AM
  4. Comparing 5 mean scores for significance
    By owen7 in forum Statistics
    Replies: 1
    Last Post: 03-29-2009, 04:50 PM
  5. reporting statistical significance & P values
    By Starr in forum Statistics
    Replies: 5
    Last Post: 11-23-2007, 04:40 AM

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts






Advertise on Talk Stats