# p-value quiz question 2

The p-value of a test with a z-score of 2.31 for a one-tailed test is 1 - 0.0104. Why is the answer said 0.010?

Hi Mai!

Thanks for reaching out!

Here, the p-value of 0.0104 is simply rounded to 0.010 for clarity and conciseness. This is often done, especially when the additional decimal places don't significantly alter the interpretation of the results.

Hope this helps.

Best,

Ivan

Thanks for replying. Based on the formula taught in p-value lesson. the p-value (one tail test) = 1 - #in the table = 1 - 0.0104 = 0.9896. But why the subtraction was not done in the solution?

Hi Mai!

The p-value is calculated is calculated slightly differently. We subtract from 1 the value from the z-table which corresponds to our z-score (2.31), not the p-value itself (0.0104), and not the z-score itself.

For a z-score of 2.31, you find the row for 2.3 in the table and then move right to the column for 0.01 (because 2.31 = 2.3 + 0.01). The cell where the row and column intersect gives you the required value.

This value is 0.9896. Therefore, the p-value is calculated as follows: 1 - 0.9896 = 0.0104.

Hope this helps.

Best,

Ivan