Refer to the accompanying data display that results from a sample of airport data speeds in Mbps. Complete parts​ (a) through​ (c) below.


a. What is the number of degrees of freedom that should be used for finding the critical value ​t a/2?
df=
​(Type a whole​ number.)


Part 2
b. Find the critical value t a/2 corresponding to a​ 95% confidence level.
t a/2=
​(Round to two decimal places as​ needed.)


Part 3
c. Give a brief general description of the number of degrees of freedom.


A. The number of degrees of freedom for a collection of sample data is the number of sample values that are determined after certain restrictions have been imposed on all data values.
B. The number of degrees of freedom for a collection of sample data is the number of​ unique, non-repeated sample values.
C. The number of degrees of freedom for a collection of sample data is the total number of sample values.
D. The number of degrees of freedom for a collection of sample data is the number of sample values that can vary after certain restrictions have been imposed on all data values.