R help - Aug 2010 - How to extract the conf.level out of t.test() data

Good afternoon everybody,

I'm writing a little function to visualise hypothesis testing. Therefore 
I need to extract the confidence level of a t-test. Here a little example:

    x <- str(t.test(1:10)

gives

    List of 9
     $ statistic  : Named num 5.74
      ..- attr(*, "names")= chr "t"
     $ parameter  : Named num 9
      ..- attr(*, "names")= chr "df"
     $ p.value    : num 0.000278
     $ conf.int   : atomic [1:2] 3.33 7.67
      ..- attr(*, "conf.level")= num 0.95
     $ estimate   : Named num 5.5
      ..- attr(*, "names")= chr "mean of x"
     $ null.value : Named num 0
      ..- attr(*, "names")= chr "mean"
     $ alternative: chr "two.sided"
     $ method     : chr "One Sample t-test"
     $ data.name  : chr "1:10"
     - attr(*, "class")= chr "htest"

Now I can use

    x$conf.int

what gives

    [1] 496.9141 499.6276
    attr(,"conf.level")
    [1] 0.95

In the example I try to extract the value 0.95 but I have no Idea how. I 
hope somebody can help me.
Thanks in advance an greetings from Berlin

Etienne

Le 09/08/10 20:39, Etienne Stockhausen a ?crit :
>
> Good afternoon everybody,
>
> I'm writing a little function to visualise hypothesis testing.
Therefore
> I need to extract the confidence level of a t-test. Here a little example:
>
> x <- str(t.test(1:10)
>
> gives
>
> List of 9
> $ statistic : Named num 5.74
> ..- attr(*, "names")= chr "t"
> $ parameter : Named num 9
> ..- attr(*, "names")= chr "df"
> $ p.value : num 0.000278
> $ conf.int : atomic [1:2] 3.33 7.67
> ..- attr(*, "conf.level")= num 0.95
> $ estimate : Named num 5.5
> ..- attr(*, "names")= chr "mean of x"
> $ null.value : Named num 0
> ..- attr(*, "names")= chr "mean"
> $ alternative: chr "two.sided"
> $ method : chr "One Sample t-test"
> $ data.name : chr "1:10"
> - attr(*, "class")= chr "htest"
>
> Now I can use
>
> x$conf.int
>
> what gives
>
> [1] 496.9141 499.6276
> attr(,"conf.level")
> [1] 0.95
>
> In the example I try to extract the value 0.95 but I have no Idea how. I
> hope somebody can help me.
> Thanks in advance an greetings from Berlin
>
> Etienne
You need the conf.level attribute, as in :

x <- t.test(1:10)
attr( x$conf.int, "conf.level" )

Romain

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try this:

x <- t.test(1:10)

x$conf.int
attr(x$conf.int, "conf.level")


I hope it helps.

Best,
Dimitris


On 8/9/2010 8:39 PM, Etienne Stockhausen wrote:
> Good afternoon everybody,
>
> I'm writing a little function to visualise hypothesis testing.
Therefore
> I need to extract the confidence level of a t-test. Here a little example:
>
> x <- str(t.test(1:10)
>
> gives
>
> List of 9
> $ statistic : Named num 5.74
> ..- attr(*, "names")= chr "t"
> $ parameter : Named num 9
> ..- attr(*, "names")= chr "df"
> $ p.value : num 0.000278
> $ conf.int : atomic [1:2] 3.33 7.67
> ..- attr(*, "conf.level")= num 0.95
> $ estimate : Named num 5.5
> ..- attr(*, "names")= chr "mean of x"
> $ null.value : Named num 0
> ..- attr(*, "names")= chr "mean"
> $ alternative: chr "two.sided"
> $ method : chr "One Sample t-test"
> $ data.name : chr "1:10"
> - attr(*, "class")= chr "htest"
>
> Now I can use
>
> x$conf.int
>
> what gives
>
> [1] 496.9141 499.6276
> attr(,"conf.level")
> [1] 0.95
>
> In the example I try to extract the value 0.95 but I have no Idea how. I
> hope somebody can help me.
> Thanks in advance an greetings from Berlin
>
> Etienne
>
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-- 
Dimitris Rizopoulos
Assistant Professor
Department of Biostatistics
Erasmus University Medical Center

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