Question

Landolt et al. (A-26) examined rates of posttraumatic stress disorder (PTSD) in mothers and fathers. Parents were interviewed 5 to 6 weeks after an accident or a new diagnosis of cancer or diabetes mellitus type I for their child. Twenty-eight of the 175 fathers interviewed and 43 of the 7.7 HYPOTHESIS TESTING: A SINGLE POPULATION VARIANCE 265 180 mothers interviewed met the criteria for current PTSD. Is there sufficient evidence for us to conclude that fathers are less likely to develop PTSD than mothers when a child is traumatized by an accident, cancer diagnosis, or diabetes diagnosis? Let a = .05.

Answer 1

Let be the proportion of fathers and be the proportion of mothers met the criteria for current PTSD.

The null and alternative hypotheses are:

This is left tailed test.

Sample proportions are:

The pooled proportion is:

The test statistic is:

For this left tailed test, p-value is:

Since , reject null hypothesis.

At 5% level of significance, there is sufficient evidence for us to conclude that fathers are less likely to develop PTSD than mothers when a child is traumatized by an accident, cancer diagnosis, or diabetes diagnosis.