Question

Nakamura et al. studied subjects with medial collateral ligament (MCL) and anterior cruciate ligament (ACL) tears. Between February 1995 and December 1997, 17 consecutive patients with combined acute ACL and grade III MCL injuries were treated by the same physician at the research center. One of the variables of interest was the length of time in days between the occurrence of the injury and the first magnetic resonance imaging (MRI). We wish to know if we can conclude that the mean number of days between injury and initial MRI is not 15 days in a population presumed to be represented by these sample data. Let ? = 0.05. 1. Set up the hypotheses. [2 points] 2. Draw a normal distribution graph with a critical value and shade the rejection region with proper size. [2 points] 3. Find the critical value from the table. [2 points]

Answer 1

Result:

Nakamura et al. studied subjects with medial collateral ligament (MCL) and anterior cruciate ligament (ACL) tears. Between February 1995 and December 1997, 17 consecutive patients with combined acute ACL and grade III MCL injuries were treated by the same physician at the research center. One of the variables of interest was the length of time in days between the occurrence of the injury and the first magnetic resonance imaging (MRI). We wish to know if we can conclude that the mean number of days between injury and initial MRI is not 15 days in a population presumed to be represented by these sample data. Let ? = 0.05.

1. Set up the hypotheses. [2 points]

2. Draw a normal distribution graph with a critical value and shade the rejection region with proper size. [2 points]

This is a two sided test.

3. Find the critical value from the table. [2 points]

Critical distribution at 0.05 level = 1.96

Rejection region: Reject Ho is z < -1.96 or z > 1.96.