Question

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

an

80​%

confidence interval estimate of the population standard deviation.

65

61

61

56

61

52

59

58

59

69

62

67

The confidence interval estimate is ?

Answer 1

Answer:

Given data,

65, 61, 61, 56, 61, 52, 59, 58, 59, 69, 62, 67

Mean = x/n

= 730/12

= 60.83

Standard deviation = sqrt((x-xbar)^2/(n-1))

= 4.67

Confidence interval = 80%

alpha = 0.2

degree of freedom = n - 1

= 12 - 1

= 11

= 17.275

= 5.5778

80% CI estimate = sqrt((n-1)s^2/) < < sqrt((n-1)s^2/)

substitute values

= sqrt((12-1)*4.67^2/17.275) < < sqrt((12-1)*4.67^2/5.5778)

= 3.73 < < 6.56