I am confusing about how to find the folloing z value At 90

I am confusing about how to find the folloing z value. At 90% confidence level, the tabulated value from the z table is z(a/2)=1.645. How do I get 1.645? I know that 1-a=0.9, so a=0.1 and a/2=0.05.

Solution

We use Z -table to figure out the value, The z value is the sum of the first row and first column, and probability is the cell of that row and column. for example, probability=0.40905 when alpha = 90% i.e AT Z = 100 =90 = 10%

As highlight the correspoing for 1.645 is 0.10027 ~ 10%