Statistics probability question

[kbat88]

If a coin is tossed three times, the likelihood of obtaining 3 heads in a row is:

a: zero
b: .500
c: 1/27
d: 2/3

Another similiar question:
If a penny is tossed 4 times and comes up heads all 4 times, the probability of heads on the 5th trial is:

Zero
1/32
.5

I am confused ---does it not have a 50/50 chance of landing on heads or tails everytime? As you can see---This question is asked several times and I can't afford to get it wrong. Is it .5 or how do you get the answer?

Thanks in advance!!!

 

[tkhunny]

If a coin is tossed three times, the likelihood of obtaining 3 heads in a row is:

a: zero
b: .500
c: 1/27
d: 2/3

Not enough information. Is it a fair coin? (½)³

Another similiar question:
If a penny is tossed 4 times and comes up heads all 4 times, the probability of heads on the 5th trial is:

Zero
1/32
.5

I am confused ---does it not have a 50/50 chance of landing on heads or tails everytime?

This is an excellent question for emphasizing "independence" of sequential trials. Previous experience does not influence future experience. This is a common fallacy for playing the lottery.

 

[kbat88]

yes it is a fair coin---
so do I understand this correctly:
it is going to be .5 or 1/2 of a chance for both problems?

 

[jennybenny02]

.5 and 1/2 are the same...
No matter how many times you toss a coin, the probability of what you will get each try will always be 1/2.

But I do remember having a lot of questions like this in my probability/stats class last sememster, I cant quite remember how they were worded. Sometimes your probability ended up being different. My questions may have asked different things included in the problem.

 

[Denis]

yes it is a fair coin---
so do I understand this correctly:
it is going to be .5 or 1/2 of a chance for both problems?

Not the 1st problem: prob is 1/2 * 1/2 * 1/2 = 1/8 (as TK says)
none of the 4 choices are correct: so CHECK your darn problem...typo?