SOLUTION: 1. A coin is being flipped 400 times. What is the probability of it landing on heads at most 170 times, rounded to the nearest tenth of a percent? This is what i've done so f

Algebra ->  Probability-and-statistics -> SOLUTION: 1. A coin is being flipped 400 times. What is the probability of it landing on heads at most 170 times, rounded to the nearest tenth of a percent? This is what i've done so f      Log On


   



Question 1202707: 1. A coin is being flipped 400 times. What is the probability of it landing on heads at most 170 times, rounded to the nearest tenth of a percent?

This is what i've done so far i just don't know what to do from this point forward.
p = 0.5
q = 1 - 0.5 = 0.5
n = 400
r = ≤ 170
mean (x ̅) = np = 400(0.5) = 200
standard deviation (σ)= √npq= √(400(0.5)(0.5))= √100=10
I've also already done the normal curve diagram and it landed exactly on -3σ.

Answer by Boreal(15235) About Me  (Show Source):
You can put this solution on YOUR website!
using the continuity correction factor, you want the z-value of (-169.5-200)/10=-3.05
probability it is less than -3.05 is 0.0011 or 0.1%
if you used what you had, it would be z<-3 which give 0.0013, or also 0.1%.