The second point is to find the probability for

the z value, which here, the 0.644 from the z tables.

The z tables, I summarize here the bigger picture

kind of quick summary of the z table, but

you will find the z table in much more details at many

textbooks as well as you can just look it up online and

you can find the more detailed ones.

And I mean by the more details, the z values if you notice I'm

giving in the first column goes from -2 all the way to 0,

but you might find bigger z tables that can go from, let's say,

-4 to 0 with have much more breakdown than just like 0.5 here and

then 0.2 and then 0.3 and 0.1 and so on.

You can find like 0.99,

0.98, 0.97 and so on.

So, the probability you will find it in this table I just gave here in

column number two and column number three and

the z values are the first column and the last column.

So once you find the z value, you look at the table and

identify where's in the table it will be located.

In our example here, the 0.644 is located

between the plus 0.6 and the positive 0.7.

So the probability will be between 0.73 and 0.76.

Or in other words, it will be between 73% to 76%.

So if you have such a situation, do a simple linear

interpolation to find what's the probability

if your z number will not be shown in the table.

So perform a linear interpolation

between all these four numbers,

the interpolation showed that the number

approximately to be around 74%.

So in this case, the value here

would be or the area underneath,

this is around 74%.

So if I want to rephrase it, the probability of completing

the project in 19 days will be 74% probability to finish it in 19 days.