Question

assume that 21-year-old men's heart rates at rest are normally distributed with a mean of 72 bpm and a standard deviation of 10 bpm. If 300 are examined, how many would you expect to have a heart rate of less than 77?

Answer 1

Its the integral of the gaussian function from -infinity to 77. You should use phi function(integral of normal gaussian) chart and also do some conversion. I don't remember the function and the conversion. But you can find them in wikipedia or some math tutorial site. that is a veri general question type. You can find many problems like this and see how to solve them.

Answer 2

http://www.wolframalpha.com/input/?i=1%2F2*erfc%28%2872-77%29%2F%2810*sqrt%282%29%29%29

Here is the calculation. The answer is 0.69 if i didn't solve it wrong

Answer 3

0.69 is the percentage. The number would be 300*0.69 = 207