Let X and Y equal the concentration in parts per billion of chromium in the blood for healthy persons and for persons with a suspected disease, respectively. Assume that the distributions of X and Y are normal. A sample of 8 observations for X have a sample mean of 15.75 and a sample variance of 46.21. A sample of 10 observations of Y have a sample mean of 23.3 and a sample variance of 92.68. Find a 90% confidence interval for the ratio of variances,

The value is  

Step-by-step explanation:

From the question we are told that

  The number of observation for X  is

  The sample mean for X  is  

  The sample variance for X is

   The number of observation for Y  is

  The sample mean for Y  is  

  The sample variance for Y is

Generally the degree of freedom for X is      

=>  

=>  

Generally the degree of freedom for X is      

=>  

=>  

From the question we are told the confidence level is  90% , hence the level of significance is    

=>  

=>  

=>  

Generally the 90% confidence interval for the ratio of variances is mathematically represented as

=>  

=>  

=>  

assuming you mean addition: addition and subtraction are reverse operations.

step-by-step explanation:

c

step-by-step explanation: