# Thread: correlation between estimation of gestational age during pregnancy by diffl methods

1. ## correlation between estimation of gestational age during pregnancy by diffl methods

what statistical test should be used for finding correlation between gestational age estimated from clinical method and that from ultrasound during pregnancy.
for eg: a mother at 36 week of gestation undergoes clinical examination and her gestational age is approximately 34 week ( symphysiofundal hieght is 34cm) and gestational age from ultrasound shows 35 week 4 days.
i have 50 such data from preg women undergoing clinical evaluation and usg at 36 weeks.
please reply urgently

2. ## Re: correlation between estimation of gestational age during pregnancy by diffl metho

If normally distributed Pearson coefficient otherwise spearman rank correlation.

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doel (09-20-2015)

4. ## Re: correlation between estimation of gestational age during pregnancy by diffl metho

sir am a novice to statistics.. am putting down 10 values... say all 10 women underwent scan at 36 wk of gestation...
clinical gestational age usg gestational age
34wk 34w 6day
35wk 34w 2day
35wk 34w 5day
33wk 34w 2day
34wk 33w 6day
36wk 35w 4day
34wk 34w 5day
35wk 34w 4day
33wk 33w 5day
34wk 35w 3day

now how do i find a correlation between these values...

5. ## Re: correlation between estimation of gestational age during pregnancy by diffl metho

You might want to convert both into days and plot two histograms to look at their distributions.

6. ## Re: correlation between estimation of gestational age during pregnancy by diffl metho

maybe a quick remark: I would do a scatterplot first, and if the realtionship is nonlinear do the Spearman anyway.

7. ## Re: correlation between estimation of gestational age during pregnancy by diffl metho

You might want to consider using a Bland-Altman plot. https://en.wikipedia.org/wiki/Bland%E2%80%93Altman_plot

8. ## Re: correlation between estimation of gestational age during pregnancy by diffl metho

Will symphysiofundal height always be gestational age as weeks (with no days)? You may eventually run two correlations, one with values as days and one with values rounded to weeks and see how these look. Since one will always be more specific than the other.

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