Homework Statement
Let $$S_{1}^2, S_{2}^2, S_{3}^2$$ be sample variances of sample size $$n_{1}, n_{2}. n_{3}$$ respectively. The populations have means $$\mu_{1}, \mu_{2}, \mu_{3}$$ respectively with common variance $$\sigma^2.$$
When is $$\pi_{1}S_{1}^2 + \pi_{2}S_{2}^2 + \pi_{3}S_{3}^2$$...
Homework Statement
Suppose that diastolic blood pressures (DBPs) for men aged 35-44 are normally distributed with a mean of 80 (mm Hg) and a standard deviation of 10. What's the probability that in a random sample of 5 subjects, 4 or more have DBPs more than 90?
Homework EquationsThe Attempt...