The dow jones industrial average has had a mean gain of 432 pear year with a standard deviation of 722. a random sample of 40 years is selected. what is the probability that the mean gain for the sample was between 200 and 550?

How do you find p(a and b) if a and b are independent events for two or more actions, such as tossing a coin twice and finding p(heads and heads)? 2. how do you find p(a or b) if a and b are independent events for one action, such as spinning a four-color spinner once and finding p(red or blue)?