Answer:


The confidence interval of standard deviation is:
to 
Step-by-step explanation:
Given

See attachment for the formatted data
Solving (a): The mean
This is calculated as:

So, we have:




Solving (b): The standard deviation
This is calculated as:




--- approximated
Solving (c): 95% confidence interval of standard deviation
We have:

So:



Calculate the degree of freedom (df)



Determine the critical value at row
and columns
and 
So, we have:
---- at 
--- at 
So, the confidence interval of the standard deviation is:
to 
to 
to 
to 
The answer is $9.50 because you need to take the total of the popcorn which is $16.50. Then subtract that from $45 and get $28.50. The last step to do is divide $28.50 by three to get your final answer= $9.50
The answer is= $9.50
Can you please tell me your question?