00:01
Assume that when adults with smartphones are randomly selected, 49 % of them use them in meetings or classes.
00:07
If 15 adult smartphone users are randomly selected, find the probability exactly 9 of them, use their smartphones in meetings or classes.
00:16
So p is equal to 0 .49, n is equal to 15, and we're trying to find the probability that x equals 9.
00:26
So we're going to do 15 combination 9 times 0 .49 to the 9th power times 0 .5 .1.
00:33
To the sixth power.
00:35
Now, combinations, we can use a scientific calculator, graphing calculator, statistical software, or we can do it by hand.
00:42
So it's 15 factorial, divided by 9 factorial, times 6 factorial.
00:49
And sometimes when i'm doing this by hand, i'll do 15 times 14 times 13 until i get to the lower number...