Find the critical value Za/2 corresponding to a 99.5% confidence level. 0.0025
2.575
2.81
1.96

The correct option is;

2.81

Step-by-step explanation:

The critical value , is found from the z score table as follows, where the the confidence level is 99.5

Therefore, we have α = 1 - 99.5/100 = 1 - 0.995 = 0.005

α/2 = 0.0025

The critical value is thus found from the z-score table value of 1 - 0.0025 = 0.9975

From the z-table, we can find the 0.9975 score on the row  with z = 2.8 where 0.9975 can be located under the 0.1 column giving the critical value as 2.81

t = 3

step-by-step explanation:

put t = 3 in this expression :

(3²-1)(3²-2)(3² - 3)(3² - 4) = 8×7×6×5 = 56×30 = 1680