Math/ genetics Q

[prsndwg]

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The probability of flipping 3 coins simultaneously and getting 2 tails and 1 head is?

edit: the answer is 1/16 as the answer key shows!!!

 

[wantVCUdental]

The probability of flipping 3 coins simultaneously and getting 2 tails and 1 head is?

The probability is 1/2 x 1/2 x 1/2 =1/8
Now to arrange the 3, you can have H, T, T
T, H, T
T, T, H
so the probability is 3/8

 

[Avery07]

The probability of flipping 3 coins simultaneously and getting 2 tails and 1 head is?

The probability of one of these events independantly is 1/2. You then use the product rule which is multiply the probabilities of each individual event by each other.

(1/2)(1/2)(1/2) = 1/8

1/8 is the chance (individual probability) for one outcome of this coin flipping (HHH, HTH, TTH, etc.)

The probability of coints being flipped in any one of these 8 orders = the sum of individual probabilities.

1/8 + 1/8 + 1/8 = 3/8

The probabiliy of this happening is 3/8.

 

[thecoolpharmboi]

So, I know on the practice tests there are measurements/unit conversions such as fl.oz.to gal., etc. Anyone know a website these unit measurement conversions?

Thanks.

 

[Avery07]

So, I know on the practice tests there are measurements/unit conversions such as fl.oz.to gal., etc. Anyone know a website these unit measurement conversions?

Thanks.

Just type it in to google search.

Search: "oz to gallon" and it gives you the conversion

http://www.google.com/search?sourceid=navclient&ie=UTF-8&rlz=1T4GGLL_enUS321US321&q=oz+to+gallon

You can do that with anything. Or even type in like 63.72 oz to gallon and it will convert that too.

 

[prsndwg]

the answer key shows it to be 1/16!!!

 

[Avery07]

the answer key shows it to be 1/16!!!

FML. I'll try to figure this one out.

 

[Avery07]

the answer key shows it to be 1/16!!!

The key has to be wrong.

Possibilities:

HHH
HHT
HTH
THH
HTT
THT
TTH
TTT

8 possibilities. There are three possibilities which include two heads and one tail. The probability of getting two heads and one tail is 3/8.

 

[Avery07]

the answer key shows it to be 1/16!!!

Are you sure you stated the question correctly?

 

[peanutb123]

Are you sure you stated the question correctly?

Avery your answer is correct... 3/8👍👍

 

[Avery07]

Avery your answer is correct... 3/8👍👍

I was going crazy sorting through my genetics notes and coming up with the same answer. 😕

Thanks for the reassurance there!

 

[Avery07]

the answer key shows it to be 1/16!!!

What book is this?

 

[peanutb123]

I was going crazy sorting through my genetics notes and coming up with the same answer. 😕

Thanks for the reassurance there!

and to the OP... since when is probability and statistics consider genetics?...

 

[Avery07]

and to the OP... since when is probability and statistics consider genetics?...

I'm not the OP but... Inheritance problems sir.

Taken from my genetics notes:

 

[prsndwg]

and to the OP... since when is probability and statistics consider genetics?...

check it out ^

 

[prsndwg]

What book is this?

campbell

 

[prsndwg]

I'm not the OP but... Inheritance problems sir.

Taken from my genetics notes:

why there is a 1/4 on the 3rd order?

 

[Avery07]

why there is a 1/4 on the 3rd order?

3/4 of the offspring will be normal (A/-)
1/4 of the offspring will be affected (a/a)

 

[Avery07]

why there is a 1/4 on the 3rd order?

The 1/4 could just as well been on the 2nd order as the 3rd order. This is just one of the X possibilities for an order including 3 normal & 1 PKU offspring.

And the picture above didn't come from my notes. I don't think gamete frequencies were part of this problem so I'm assuming this problem requires hardy-weinberg equilibrium? Otherwise with those gamete frequencies, 1/4 of the population would not be PKU.

 

[Streetwolf]

I'm not the OP but... Inheritance problems sir.

Taken from my genetics notes:

You never said what the probability of having PKU actually is. Is it a 1/4 chance? Just because you are looking for 1/4 of the children to have it doesn't mean that 1/4 is the probability.

Going by the standard Punnett square perhaps it is, but you would want to make a note of that. If there were 5 children then you'd have a better example.

prsndwg: The probability of being normal is 3/4 (apparently, see note above). The probability of having PKU is 1/4. So in 4 children, the probability of ANY one and ONLY one of them having the disease is (3/4)(3/4)(3/4)(1/4). Avery07 just put the 1/4 in the third position.

Edit: Okay you put up a Punnett square with different probabilities. You have to use those and not 3/4, 1/4.

 

[prsndwg]

3/4 of the offspring will be normal (A/-)
1/4 of the offspring will be affected (a/a)

got it thanks

 

[UCB05]

The equation for an "exactly x out of y times" question is something like
nCr p^i q^(n-r)
where p is your favored outcome, q is your unfavored outcome, r is your favored frequency. nCr represents the number of such combinations allowed

For a 3-pick-2 question, it will be
3C2 (.5^2)(.5^1)
or
3(1/2)(1/2)(1/2)

In another example: You throw a die 10 times. what is the probability that it will land on "3" exactly 2 times?
The probability of a 3 landing is 1/6, and the probability of not landing is 5/6. The probability then is: 10C2 (1/6)^2 (5/6)^8