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Apple Google Getting Started Most Visited- , Blackboard Learn Blackboard Learn Homework: Section 7.4 Estimating Population Standard Dev Ex. Score: 0 of 1 pt HW Score: 16.67% (1 of 6 pts) 3 of 6 complete Use the given information to find the number of degrees of freedom, the critical values xi and , and the confidence interval estimate of. It is reasonable to assume that a simple random sample has been selected from a population with a normal distribution. Platelet Counts of women 95% confidence; n·26, s 65.4. Click the icon to view the table of Chi-Square critical values. eraf- (Type a whole number.)

Explanation / Answer

a)

Note that
                              
df = n - 1 =    25   [ANSWER]      

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b)

alpha = (1 - confidence level)/2 =    0.025          
              
Then the critical values for chi^2 are              
              
chi^2(alpha/2) =    40.64646912 = XR^2          
chi^2(alpha/2) =    13.11972002 = XL^2          

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c)

Thus, as              
              
lower bound = (n - 1) s^2 / chi^2(alpha/2) =    2630.708209          
upper bound = (n - 1) s^2 / chi^2(1 - alpha/2) =    8150.250142          
              
Thus, the confidence interval for the variance is              
              
(   2630.708209   ,   8150.250142   )
              
Also, for the standard deviation, getting the square root of the bounds,              
              
(   51.29043   ,   90.27873583   ) [ANSWER, CONFIDENCE INTERVAL FOR SIGMA]

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