# Solving probabilities that involves percentage.

• Sep 30th 2012, 07:20 PM
fara
Solving probabilities that involves percentage.
I'm weak when it comes to solving probability questions that has to do with percentage. please help me.

1. Muscular dystrophy is a genetically controlled disease. The probability of having this disease in any new born of a specific parents is 25%. If the couple has 5 children, find the probabilities that:
(a) 5 will have a muscular dystrophy
(b) Fewer than 2 will have a muscular dystrophy

2. If 20% of the bolts produced by a machine are defective, determine the probability that out of 4 bolts:
(a) 1 is defective
(b) None of the bolts is defective
At most 2 bolts will be defective

tq
• Sep 30th 2012, 07:26 PM
Prove It
Re: Solving probabilities that involves percentage.
Quote:

Originally Posted by fara
I'm weak when it comes to solving probability questions that has to do with percentage. please help me.

1. Muscular dystrophy is a genetically controlled disease. The probability of having this disease in any new born of a specific parents is 25%. If the couple has 5 children, find the probabilities that:
(a) 5 will have a muscular dystrophy
(b) Fewer than 2 will have a muscular dystrophy

2. If 20% of the bolts produced by a machine are defective, determine the probability that out of 4 bolts:
(a) 1 is defective
(b) None of the bolts is defective
At most 2 bolts will be defective

tq

a) Each child has a 1/4 chance of getting the disease, so the probability of all of them having the disease is 1/4 x 1/4 x 1/4 x 1/4 x 1/4 = (1/4)^5.
• Sep 30th 2012, 07:52 PM
MaxJasper
Re: Solving probabilities that involves percentage.
Quote:

Originally Posted by fara
1. Muscular dystrophy is a genetically controlled disease. The probability of having this disease in any new born of a specific parents is 25%. If the couple has 5 children, find the probabilities that:
(a) 5 will have a muscular dystrophy
(b) Fewer than 2 will have a muscular dystrophy

2. If 20% of the bolts produced by a machine are defective, determine the probability that out of 4 bolts:
(a) 1 is defective
(b) None of the bolts is defective
At most 2 bolts will be defective
tq

HINTS:

1b) 0.63281

2a) 0.4096
2b) 0.4096
2c) 0.9728
• Sep 30th 2012, 07:57 PM
Prove It
Re: Solving probabilities that involves percentage.
Quote:

Originally Posted by MaxJasper
HINTS:

1b) 0.63281

2a) 0.4096
2b) 0.4096
2c) 0.9728

Those aren't hints, those are answers. Answers which the OP most likely already has if he/she looks in the back of the book for.

A hint is something which gives the OP some direction to solve the problem him/herself. Such as for 1.b) you will need to use the Binomial Distribution.