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If Anna flips 8 coins, what is the probability that she gets more heads than tails?

 Apr 19, 2015

Best Answer 

 #2
avatar+250 
+10

Gotta be careful with how the question is worded titanium.

Probability of getting more heads than tails in a total of 8 flips is the probability of getting 5 heads, 6 heads, 7 heads, or 8 heads.

 

Almost identical problem to this: http://web2.0calc.com/questions/a-fair-coin-is-flipped-7-times-what-is-the-probability-that-at-least-5-of-the-flips-come-up-heads

Your final answer should be about 0.363

 Apr 19, 2015
 #1
avatar+2972 
0

mmmmm, probably 1/2 cuz its only heads and tails, so 8 coin flips divided by the 2 sides (in this case, heads and tails)=4 and half of 8 as you know is 4, so the probability overall is 1/2

-Titanium Rome

 Apr 19, 2015
 #2
avatar+250 
+10
Best Answer

Gotta be careful with how the question is worded titanium.

Probability of getting more heads than tails in a total of 8 flips is the probability of getting 5 heads, 6 heads, 7 heads, or 8 heads.

 

Almost identical problem to this: http://web2.0calc.com/questions/a-fair-coin-is-flipped-7-times-what-is-the-probability-that-at-least-5-of-the-flips-come-up-heads

Your final answer should be about 0.363

Brodudedoodebrodude Apr 19, 2015
 #3
avatar+118616 
0

Good explanation there Brodude :)

 Apr 20, 2015
 #4
avatar+355 
+6

8C5 + 8C6 + 8C7 + 8C8

 

56 + 28 + 8 + 1

 

93

 

Put it over 256

 

93/256<-------Answer

 

93/256 is approximatly 0.363

 

Using Casework

 

Case 1:5 heads, 3 tails

8C5 * (1/2)^8 = 7/32

 

Case 2:  6 heads, 2 tails

8C6 * (1/2)^8 = 7/64

 

Case 3: 7 heads, 1 tails

8C1 * (1/2)^8 = 1/32

 

Case 4: All 8 heads

(1/2)^8 = 1/256

 

7/32 + 7/64 + 1/32 + 1/256 <-------_Add them up

 

93/256

 Dec 31, 2016

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