Question

If you obtain a P value for a 2-tailed t-test, how does this convert to a 1-tailed test?

a. Multiply by 2
b. Divide by 2
c. Square the P value
d. Use a different significance level

Answer 1

To convert a two-tailed p-value to a one-tailed p-value in a t-test, divide the two-tailed p-value by 2 as a one-tailed p-value considers only one tail of the distribution.

Step-by-step explanation:

To convert a two-tailed p-value to a one-tailed p-value, you would divide by 2. This is because a two-tailed p-value accounts for the probability of extreme values in both tails of the distribution, whereas a one-tailed p-value considers only one tail.

When you use technology to calculate the p-value, it's calculated using a t distribution with degrees of freedom based on your sample size, and represents the combined area in both tails for a two-tailed test. For a one-tailed test, the alternative hypothesis (Ha) dictates whether you are looking at the left or the right tail.

If the original two-tailed p-value is 0.0716, then converting it to a one-tailed p-value would mean you take 0.0716 and divide by 2, resulting in 0.0358.