Thread: 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

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.

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

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.