Answer:
b. 2.01 < σ < 2.81
Step-by-step explanation:
The 90% confidence interval for the population standard deviation is calculated as:
< σ < 
Where n is equal to 51, s is equal to 2.34,
is 10%,
is the value for the Chi squared distribution with n-1 degrees of freedom that has a probability of
in the right tail and
is the value for the Chi squared distribution with n-1 degrees of freedom that has a probability of
in the right tail.
So, replacing n by 51, s by 2.34,
by 67.50 and
by 34.76, we get that the The 90% confidence interval is equal to:
< σ <
2.01 < σ < 2.81
-3x+1+10x=x+4
1+7x=x+4
6x=3
x=.5
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