In: Math
Use the given information to find the number of degrees of freedom, the critical values chi Subscript Upper L Superscript 2 and chi Subscript Upper R Superscript 2, and the confidence interval estimate of sigma. It is reasonable to assume that a simple random sample has been selected from a population with a normal distribution. Nicotine in menthol cigarettes 80% confidence; n=27, s=0.29 mg.
Solution :
Given that,
s = 0.29
s2 = 0.0841
2L
= 
2
/2,df
= 35.563
2R
= 
21 - 
/2,df = 17.292
The 80% confidence interval for 
 is,
(n
- 1)s2 / 
2
/2
< 
 < 
(n - 1)s2 / 
21 - 
/2
  
26
* 0.0841 / 35.563 < 
 < 
26 * 0.0841 / 17.292
0.25 < 
 < 0.36
(0.25 , 0.36)