A geologist examines 14 geological samples for iron concentration. The mean iron concentration for the sample data is 0.181 cc/cubic meter with a standard deviation of 0.0318. Determine the 90% confidence interval for the population mean iron concentration. Assume the population is approximately normal.

Step 1 of 2:

Find the critical value that should be used in constructing the confidence interval. Round your answer to three decimal places.

Step 2 of 2:

Construct the 90%90% confidence interval. Round your answer to three decimal places.