Question

Fission tracks are trails found in uranium-bearing minerals, left by fragments released during fission events. An article reports that fifteen tracks on one rock specimen had an average track length of 10 μm with a standard deviation of 2 μm. Assuming this to be a random sample from an approximately normal population, find a 99% confidence interval for the mean track length for this rock specimen. Round the answers to three decimal places.

The 99% confidence interval is

Answer 1

c )solution

Given that,

= 10

s =2

n = 15

Degrees of freedom = df = n - 1 = 15- 1 = 14

At 99% confidence level the t is ,

= 1 - 99% = 1 - 0.99 = 0.01

/ 2 = 0.01 / 2 = 0.005

t /2  df = t0.005,14 = 2.977 ( using student t table)

Margin of error = E = t/2,df * (s /n)

=2.977 * (2 / 15) = 1.537

The 99% confidence interval mean is,

- E < < + E

10 - 1.537 < <10 + 1.537

8.463 < < 11.537

(8.463 , 11.537)