Thread: am i suppose to use binomial to solve?

1. 75% of a community voted Jay Cool as their favourite singer. A random sample of 25 people was taken from this large population. Estimate the chance that
a. everybody in the sample voted him as their favourite singer.
b. exactly 10 individuals in the sample voted him as their favourite singer.
2. 12 students from a school are shortlisted as players for a basketball team. If 15% of the school population were found to be left handed, calculate the probability of
a. all the players being right handed.
b. exactly half of the team is left handed

3. Suppose 70% of a herd of cattle is infected with a particular disease. Let Y be the number of diseased cattle in a sample of size 10. What is the probability of Y

• being less than 2?

b. being more than 8?
c. being between 2 to 8 (inclusive)?

4. Consider a family consisting of 8 children. Assuming that the chance of male and female births is the same. What is the probability of the children

• consisting of at least 1 boy?
• consisting of at least 1 girl and 1 boy?

5. Considering the tossing of a pair of fair dice together, what is the probability of

• obtaining a total of 7 in a single toss?
• obtaining a total of 7 exactly twice in 6 tosses?

Originally Posted by dorwei92

1. 75% of a community voted Jay Cool as their favourite singer. A random sample of 25 people was taken from this large population. Estimate the chance that
a. everybody in the sample voted him as their favourite singer.
b. exactly 10 individuals in the sample voted him as their favourite singer.

Mr F says: Use the Binomial distribution. n = 25, p = 0.75.

2. 12 students from a school are shortlisted as players for a basketball team. If 15% of the school population were found to be left handed, calculate the probability of
a. all the players being right handed.
b. exactly half of the team is left handed

Mr F says: Use the Binomial distribution. n = 12, p = 0.15. Calculate Pr(X = 0) and Pr(X = 6).



3. Suppose 70% of a herd of cattle is infected with a particular disease. Let Y be the number of diseased cattle in a sample of size 10. What is the probability of Y

• being less than 2?

b. being more than 8?
c. being between 2 to 8 (inclusive)?

Mr F says: Use the Binomial distribution. n = 10, p = 0.7.


4. Consider a family consisting of 8 children. Assuming that the chance of male and female births is the same. What is the probability of the children

• consisting of at least 1 boy?
• consisting of at least 1 girl and 1 boy?

Mr F says: Use the Binomial distribution. n = 8, p = 0.5. Calculate Pr(X > 0) = 1 - Pr(X = 0). For the second, I don't get it ..... Do you mean BG and the other 6 don't matter?



5. Considering the tossing of a pair of fair dice together, what is the probability of

• obtaining a total of 7 in a single toss? Mr F says: Draw a grid and count the favourable outcomes.
• obtaining a total of 7 exactly twice in 6 tosses? Mr F says: Use the Binomial distribution. n = 6, p = probability calculated above.

It might pay to review the Binomial distribution.

i don't understand q2. why is the Pr(X=0) to find # of players being right handed?

Originally Posted by dorwei92

i don't understand q2. why is the Pr(X=0) to find # of players being right handed?

If one is not left-handed then the person must be right-handed.

so can i assume that X = people who're left handed ?
thus, X =0 to find the probability of being right handed?

Originally Posted by dorwei92

so can i assume that X = people who're left handed ? thus, X =0 to find the probability of being right handed?

The probability that no one on the team is left-handed is the probability that everyone on the team is right-handed.