According to a study by the Centers for Disease Control, the national mean hospital stay after childbirth is 2.1 days. Reviewing records at her own hospital, a hospital administrator calculates that the mean hospital stay for a random sample of 81 women after childbirth is 2.3 days with a standard deviation of 1.2 days.
Test the claim that the mean hospital stay after childbirth for this hospital is significantly longer than the national mean of 2.1 days.
Is this a one-tailed or a two-tailed test?
A) one-tailed to the right
B) one-tailed to the left
C) two-tailed
A?
You're right.
Yes, you are correct. In this case, the test is one-tailed to the right.
To understand why it is a one-tailed test in this scenario, let's break down the information given. The claim being tested is whether the mean hospital stay for this hospital is significantly longer than the national mean of 2.1 days.
One-tailed tests are used when there is a specific directionality involved in the hypothesis. In this case, the hypothesis is that the mean hospital stay for this hospital is longer than the national mean, indicating a rightward direction on the distribution.
Since we are only interested in one specific direction (longer than 2.1 days), the test is one-tailed to the right.