February, 2003
© 2000, 2001, 2003 Scott S. Emerson, M.D., Ph.D.
Conf int: Sampling density tail beyond observed value
We want a 95% CI for the observed sample mean of 0.4.
If the true treatment effect corresponds to a mean
of 0, the probability of observing a sample mean greater than 0.4
is 0.217, which is between 0.025 and 0.975
·Hence,
0 is in the 95% confidence interval
If the true treatment effect corresponds to a mean of 1.43, the
probability of observing a sample mean greater than 0.4
is 0.978, which is not between 0.025 and 0.975
·Hence, 1.43 is not in the 95% confidence interval