Notice: On April 23, 2014, Statalist moved from an email list to a forum, based at statalist.org.
[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]
Re: st: Interpretation of Two-sample t test with equal variances?
From
Gwinyai Masukume <[email protected]>
To
[email protected]
Subject
Re: st: Interpretation of Two-sample t test with equal variances?
Date
Wed, 20 Mar 2013 07:04:38 +0200
Thank you Richard. Yes, I guess the t-test suggests the counter
intuitive though it probably won’t change things much.
How can I reverse the situation?
I ran a logistic regression for binary outcomes as you suggested:
Essentially no significance is shown?
. logit mode_delivery age
Iteration 0: log likelihood = -159.58665
Iteration 1: log likelihood = -159.34203
Iteration 2: log likelihood = -159.34197
Iteration 3: log likelihood = -159.34197
Logistic regression Number of obs = 250
LR chi2(1) = 0.49
Prob > chi2 = 0.4842
Log likelihood = -159.34197 Pseudo R2 = 0.0015
-------------------------------------------------------------------------------
mode_delivery | Coef. Std. Err. z P>|z| [95% Conf. Interval]
--------------+----------------------------------------------------------------
age | .0155454 .0222368 0.70 0.485 -.028038 .0591288
_cons | -1.133737 .6630978 -1.71 0.087 -2.433385 .1659111
-------------------------------------------------------------------------------
With thanks,
Gwinyai
On 3/20/13, Richard Williams <[email protected]> wrote:
> Your t-test seems to suggest that age is affected
> by mode of delivery, rather than mode of delivery
> is affected by age. It probably won't change
> things much but this makes more sense to me given your hypotheses:
>
> logit mode_delivery age
>
> At 11:08 PM 3/19/2013, Gwinyai Masukume wrote:
>>Dear Stata list,
>>
>>I would like to double check the interpretation and appropriateness of
>>the following statistical test I performed.
>>My alternate hypothesis is that, “There is a difference in the baby’s
>>mode of delivery depending on maternal age” And the null hypothesis is
>>that, “There is no difference in the baby’s mode of delivery depending
>>on maternal age”
>>Looking at the output “Ha: diff != 0, Pr(|T| > |t|) = 0.4861”, I
>>fail to reject the null hypothesis and conclude that, “There is no
>>difference in the baby’s mode of delivery depending on maternal age”
>>
>>Is this a sound and appropriate interpretation?
>>
>>. *** Doing a T-test
>>. ttest age, by(mode_delivery)
>>
>>Two-sample t test with equal variances
>>------------------------------------------------------------------------------
>> Group | Obs Mean Std.
>> Err. Std. Dev. [95% Conf. Interval]
>>---------+--------------------------------------------------------------------
>> Vaginal
>> | 166 28.83072 .4696729 6.051313 27.90338 29.75807
>>C/sectio | 84 29.39524 .6579862 6.030543 28.08653
>> 30.70395
>>---------+--------------------------------------------------------------------
>>combined | 250 29.0204 .3818851 6.038134 28.26826
>> 29.77254
>>---------+--------------------------------------------------------------------
>> diff
>> | -.5645152 .8093331 -2.158558 1.029528
>>------------------------------------------------------------------------------
>> diff = mean(Vaginal) -
>> mean(C/sectio) t = -0.6975
>>Ho: diff = 0 degrees of freedom =
>> 248
>>
>> Ha: diff < 0 Ha: diff != 0 Ha: diff >
>> 0
>> Pr(T < t) = 0.2431 Pr(|T| > |t|) =
>> 0.4861 Pr(T > t) = 0.7569
>>
>>With kind regards,
>>Gwinyai
>>
>>*
>>* For searches and help try:
>>* http://www.stata.com/help.cgi?search
>>* http://www.stata.com/support/faqs/resources/statalist-faq/
>>* http://www.ats.ucla.edu/stat/stata/
>
> -------------------------------------------
> Richard Williams, Notre Dame Dept of Sociology
> OFFICE: (574)631-6668, (574)631-6463
> HOME: (574)289-5227
> EMAIL: [email protected]
> WWW: http://www.nd.edu/~rwilliam
>
>
> *
> * For searches and help try:
> * http://www.stata.com/help.cgi?search
> * http://www.stata.com/support/faqs/resources/statalist-faq/
> * http://www.ats.ucla.edu/stat/stata/
>
*
* For searches and help try:
* http://www.stata.com/help.cgi?search
* http://www.stata.com/support/faqs/resources/statalist-faq/
* http://www.ats.ucla.edu/stat/stata/