Question

CONFIDENCE INTERVAL IN STATS MODE. At a particular location along a highway, the speed limit is 65 mph. The speeds of vehicles are Normally distributed with sigma equals 6 m p h, but is the mean speed 65 mph? A state trooper measures the speeds of a random sample of 16 passing vehicles. The average speed for this sample is x with bar on top= 67.8 mph. Compute a 90% confidence interval for the mean speed at this location.

lower limit =

and upper limit is =

The margin of error of the estimate =

CONFIDENCE INTERVAL IN DATA MODE. (Enter data into L1 first) Many areas in Minnesota have high levels of arsenic in the ground water. Because arsenic can cause health problems, a random sample of 8 residents in one of these areas had their arsenic blood concentrations measured. Arsenic blood concentrations are Normally distributed with a standard deviation of sigma= 1.5 micrograms per deciliter. Their results are 1.7, 2.7, 3.9, 3.0, 5.0, 5.7, 4.5, 2.3 Give a 99% confidence interval for the mean blood arsenic concentration in this region.

Interval: lower limit =

and Upper limit =

The margin of error of this estimate is

Answer 1

Confidence Interval :-



Lower Limit =
Lower Limit = 65.3327
Upper Limit =
Upper Limit = 70.2673
90% Confidence interval is ( 65.3327 , 70.2673 )

The margin of error of the estimate =

	Values ( X )
	1.7	3.61
	2.7	0.81
	3.9	0.09
	3	0.36
	5	1.96
	5.7	4.41
	4.5	0.81
	2.3	1.69
Total	28.8	13.74

Mean

Standard deviation

Sample variance = 1.9629

Confidence Interval :-



Lower Limit =
Lower Limit = 2.234
Upper Limit =
Upper Limit = 4.966
99% Confidence interval is ( 2.234 , 4.966 )

The margin of error of this estimate is