In: Statistics and Probability
An iceberg consists of frozen freshwater that has broken away from a glacier, and could be more than 15,000 years old. Icebergs in the Grand Banks area are estimated to weigh between 100,000 and 200,000 tons. Suppose a team of scientists aboard a research vessel operating in the Grand Banks area selects a random sample of 49 icebergs. The height is carefully measured for each, and the sample mean is x = 101 meters. Assume σ = 25 meters.
(a) Find a 99% confidence interval for the mean height of icebergs in the Grand Banks area (in meters). (Round your answers to four decimal places.)
(____________ , __________)meters
Solution :
Given that,
Point estimate = sample mean =
= 101
Population standard deviation =
= 25
Sample size = n =49
At 99% confidence level the z is ,
= 1 - 99% = 1 - 0.99 = 0.01
/ 2 = 0.01 / 2 = 0.005
Z/2 = Z0.005 = 2.576
Margin of error = E = Z/2* ( /n)
= 2.576 * ( 25/ 49)
= 9.2000
At 99% confidence interval estimate of the population mean is,
- E < < + E
101 - 9.2000< < 101 +9.2000
91.8000< < 110.2000
(91.8000 , 110.2000)