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October 21, 2014

October 21, 2014

Posted by **Dawn** on Saturday, August 21, 2010 at 6:18am.

Assume that these observations are an SRS from the late Cretaceous atmosphere. What is the mean percent of nitrogen in ancient air with a 90% confidence level?

Hint: uses one-sample t confidence

- Statistics -
**MathGuru**, Sunday, August 22, 2010 at 8:24amFormula: CI90 = mean + or - (t-value)(sd/√n)

Determine the t-value from a t-table. Use degrees of freedom 8 (which is sample size minus one). You will also need to determine the mean by adding up the values and dividing them by the sample size. Find sd (standard deviation) as well. Substitute those values into the formula to calculate the confidence interval.

I hope this will help get you started.

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