1. Hi,

Sample size iz n=9. I have a values in percentage which indicate a certain deviation (either positive or negative). For example:

-1.25%, +1.63% ... etc.

I get the 95% CI that has lower bound negative and upper bound positive. Can this be true or something is wrong?

Many thanks.

2.

3. Without knowing what those percentages represent, I couldn't really say, but it's certainly possible for some ways of calculating confidence intervals to put the range out of bounds. You could try recalculating things in a logarithmic domain if you know your numbers must be positive.

4. Percentages represent the change in price. The values are: -1.25%, +1.63%, +0,22%, -0,56%, +21,54%, -1,83%, -1,63%, -0,7%, -0,37%.

My results are 95% CI = 1.89% +/- 5.71%. Is this correct?

P.S. I have used t distribution.

Best regards,

5. Looks about right to me, or at least I got the same answer (though 5.719 should probably be rounded to 5.72). Since prices can certainly drop (and you even have negative samples), a negative lower bound is certainly reasonable.

6. Thank you for your effort.

One more thing, how to interpret the results given the small sample size?

Best regards.

7. That would depend on how you got the sample I think. Generally though, you would expect another sample to fall within those bounds 95% of the time.

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