If you're seeing this message, it means we're having trouble loading external resources on our website.

If you're behind a web filter, please make sure that the domains *.kastatic.org and *.kasandbox.org are unblocked.

# Using a table to estimate P-value from t statistic

In a significance test about a population mean, we first calculate a test statistic based on our sample results. We can then use a table to estimate the p-value based on that test statistic using a t distribution with n-1 degrees of freedom.

## Want to join the conversation?

• Why should we include the area above and below the 2.75 t value when t = a positive value?
• This is because our alternative hypothesis is that mu is not equal to 0, so we need to look at cases at both extremes from 0.

If the Ha were stating that mu>0, then we would only be concerned with the upper end.

If the Ha were stated that mu<0, then we would be concerned with the lower end.
• Anywhere I can get this t* table?
• Here is a link to the t-table I commonly use:
https://t-tables.net/
(1 vote)
• According to my statistic book reference tables.... In this lesson he is using the t-table for a one-tailed test, but according to this question he should be using the t-values needed for rejection of the null hypothesis for the two-tailed test.

right?
• Yes, but he multiplied the probability of getting the sample mean or higher by two to get the p-value by using the fact that the t-distribution is symmetric, giving the same result.
• what do you do when a t-value is negative? would you look it up the same way, but find the p-value using 1-P-value(t)?
• You use the closest number to the value on the table.
• The critical calues - t-statistictable in my textbook doesn't look like this. Instead it has a 95% and 99% significnce level column. Can anyone tell me why?