4 simple probability questions

Question

1 . Approximately 72% of the students in this class make less than $20,000 a year. If 7 students are randomly selected, find the probability that more than 3 students make less than $20,000 a year.

 

2. Approximately 14% of the students in this class make between $20,000 and $29,999 a year. If 7 students are randomly selected, find the probability that at most 3 students make between $20,000 and $29,999 a year.

 

3. Approximately 7% of the students in this class make between $30,000 and $39,999 a year. If 7 students are randomly selected, find the probability that no more than 2 students make between $30,000 and $39,999 a year.

 

4. Approximately 2% of the students in this class make between $40,000 and $49,999 a year. If 7 students are randomly selected, find the probability that exactly 1 student make between $40,000 and $49,999 a year.

Answer 1

You can answer all of these by using a binomial distribution.

 

For example in (a) n=7 and p=.72 .