• One-tail test
We find the value in the z table when z = 1.25:
we can see that it is 0.8944. As it is a one-tail test, we have to subtract from 1:
Then, in a one-tail test, when z = 1.25, the p-value = 0.1056.
• Two-tail test
We also have to know the value of the z-table when z = 1.25. As we already got it, we know that it is 0.8944. Then we also have to subtract it from 1, which we also know this result (0.1056).
However, as this is a two-tail test, the difference is that we have to multiply this value times two:
And that would be our p-value.
Answer:
• One-tail test p-value: 0.1056
,
• Two-tail test p-value: 0.2112