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From |
David Hoaglin <dchoaglin@gmail.com> |

To |
statalist@hsphsun2.harvard.edu |

Subject |
Re: st: Interpretation of Two-sample t test with equal variances? |

Date |
Wed, 20 Mar 2013 10:02:44 -0400 |

Gwinyai, In your first message you posed the question of whether the mode of delivery depended on (or was related to) mother's age. The logistic regression is an appropriate way to approach that question. The output says that, in your data, the odds of a C/section increase with mother's age, but the rate of increase does not differ significantly from zero. That is, the risk of a C/section is not related to mother's age. You may want to do a little diagnostic checking, to make sure that the logit model is a satisfactory summary of your data. You could split the age range into intervals (with a reasonable total sample size in each interval), and calculate the percentage of C/sections in each category. Does either group of mothers contain any unusually low or unusually high ages? I hope this discussion is helpful. David Hoaglin On Wed, Mar 20, 2013 at 1:04 AM, Gwinyai Masukume <parturitions@gmail.com> wrote: > 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 * * 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/

**Follow-Ups**:**Re: st: Interpretation of Two-sample t test with equal variances?***From:*Nick Cox <njcoxstata@gmail.com>

**References**:**st: Interpretation of Two-sample t test with equal variances?***From:*Gwinyai Masukume <parturitions@gmail.com>

**Re: st: Interpretation of Two-sample t test with equal variances?***From:*Richard Williams <richardwilliams.ndu@gmail.com>

**Re: st: Interpretation of Two-sample t test with equal variances?***From:*Gwinyai Masukume <parturitions@gmail.com>

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