You intend to estimate a population mean

with the following sample.

18

8.8

27

11.6

16.2

22.3

25.6

You believe the population is normally distributed. Find the 90% confidence interval. Enter your answer as anopen-interval(i.e., parentheses) accurate to two decimal places (because the sample data are reported accurate to one decimal place).

90% C.I. =

Answer should be obtained without any preliminary rounding. However, the critical value may be rounded to 3 decimal places.