Answer:
0.561
Step-by-step explanation:
To solve this problem we must resort to external information that I will leave attached with the answer, it is a table that for each value of n, gives us the critical values.
Returns the critical values for both the significant levels of 0.01 and 0.05.
If we go to the table we know that when n = 20 and the significant level is 0.01, the corresponding critical value is: 0.561