My data shows 95% CI = [-1.07, -0.40], what does the negative sign indicate and how do I interpret the data? as I think it is significant for not capturing the value of 0.
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1$\begingroup$ Welcome anna. Could you be more precise? For what parameter is the confidence interval? Usually, if the confidence interval does not include the null value, the result is said to be statistically significant. If the 95%-CI does not include the null, the corresponding $p$-value is < 0.05 and you have evidence that the corresponding parameter is different (in your case smaller) than the null value. $\endgroup$– COOLSerdashCommented May 13, 2013 at 7:54
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The interpretation will depend on the specifics of your situation but, generally speaking, the negative sign does not fundamentally change anything. Formally, 95% of these confidence intervals should contain the true parameter. Also, with the same data, the corresponding test would yield a p-value under 5% for all values outside of the confidence interval and over 5% for all values inside this interval.
For example, if this is a confidence interval for a difference (e.g. t-test or contrast/pairwise differences in an ANOVA), you can indeed say that this difference is significantly different from 0 and that the reference group has a higher mean than the other one (not that you should always test if something is different from 0, this is just an habit in many disciplines but by no means a necessity).
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$\begingroup$ I conducted a contrast test on XECI to test whether the average of under 30, 30-39 and 40-49 would have a higher DV than 50+ and it gave me those negative values. Does it necessarily indicate that 50+ has a higher DV? $\endgroup$– annaCommented May 14, 2013 at 1:02
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1$\begingroup$ @anna It would depend on how you coded your contrast (or how your software did it for you). You could perhaps add all this information to your question to make it more interesting and attract more attention to it. A little more context could also be useful (what's XECI?) $\endgroup$– GalaCommented May 14, 2013 at 6:35