Listed below are speeds​ (mi/h) measured from traffic on a busy highway. This simple random sample was obtained at​ 3:30 P.M. on a weekday. Use the sample data to construct a 80% confidence interval...

Listed below are speeds​ (mi/h) measured from traffic on a busy highway. This simple random sample was obtained at​ 3:30 P.M. on a weekday. Use the sample data to construct a 80% confidence interval estimate of the population standard deviation. 61,60,60,56,60,53,59,58,59,70,58,67

The confidence interval estimate is__mi/h<><__mi>

Round to one decimal place as needed.