Question

a) A random sample of 19 cans of peach halves has a mean weight of 16 ounces and standard deviation of 0.4 ounces. A)Find a 95 % confidence interval for a true standard deviation of the weights of all cans of peach halves.

B) What would be the confidence interval for a true standard deviation if the sample size was 47 ? Confidence interval: ( , )

Answer 1

A) Now , df=degrees of freedom=n-1=19-1=18

The critical values are ,

; The Excel function is , =CHIINV(0.025,18)

; The Excel function is , =CHIINV(0.975,18)

Therefore , the 95% confidence interval for a true standard deviation of the weights of all cans of peach halves is ,

B) Now , df=degrees of freedom=n-1=47-1=46

The critical values are ,

; The Excel function is , =CHIINV(0.025,46)

; The Excel function is , =CHIINV(0.975,46)

Therefore , the 95% confidence interval for a true standard deviation of the weights of all cans of peach halves is ,

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