Question

It is known that 15% of the population is afraid of being alone at night. If...

It is known that 15% of the population is afraid of being alone at night. If a random sample of 20 Americans is selected, what is the probability that :

a. Exactly 6 of them are afraid?

b. Less than 2 of them are afraid?

c. At least 1 of them is afraid?

d. What is the standard deviation for the number of people that are afraid?

Homework Answers

Answer #1

a)

Here, n = 20, p = 0.15, (1 - p) = 0.85 and x = 6
As per binomial distribution formula P(X = x) = nCx * p^x * (1 - p)^(n - x)

We need to calculate P(X = 6)
P(X = 6) = 20C6 * 0.15^6 * 0.85^14
P(X = 6) = 0.0454


b)


Here, n = 20, p = 0.15, (1 - p) = 0.85 and x = 2
As per binomial distribution formula P(X = x) = nCx * p^x * (1 - p)^(n - x)

We need to calculate P(X <= 2).
P(X <2) = (20C0 * 0.15^0 * 0.85^20) + (20C1 * 0.15^1 * 0.85^19)
P(X <2) = 0.0388 + 0.1368
P(X < 2) = 0.1756

c)

Here, n = 20, p = 0.15, (1 - p) = 0.85 and x = 1
As per binomial distribution formula P(X = x) = nCx * p^x * (1 - p)^(n - x)

We need to calculate P(X >= 1).

We need to calculate P(X <= 0).
P(X <= 0) = (20C0 * 0.15^0 * 0.85^20)
P(X <= 0) = 0.0388
P(X <= 0) = 0.0388

P(X>=1) = 1- P(x< =0)
=1 - 0.0388
= 0.9612


d)
std.dev = sqrt(npq)
=sqrt(20 * 0.15 * 0.85)
= 1.5969

c)

Know the answer?
Your Answer:

Post as a guest

Your Name:

What's your source?

Earn Coins

Coins can be redeemed for fabulous gifts.

Not the answer you're looking for?
Ask your own homework help question
Similar Questions
According to a study conducted by an​ organization, the proportion of Americans who were afraid to...
According to a study conducted by an​ organization, the proportion of Americans who were afraid to fly in 2006 was 0.10. A random sample of 1,100 Americans results in 99 indicating that they are afraid to fly. Explain why this is not necessarily evidence that the proportion of Americans who are afraid to fly has decreased. Select the correct choice below​ and, if​ necessary, fill in the answer box to complete your choice. A. This is not necessarily evidence that...
63% of all Americans live in cities with population greater than 100,000 people. If 45 Americans...
63% of all Americans live in cities with population greater than 100,000 people. If 45 Americans are randomly selected, find the probability that a. Exactly 27 of them live in cities with population greater than 100,000 people. b. At most 27 of them live in cities with population greater than 100,000 people. c. At least 30 of them live in cities with population greater than 100,000 people. d. Between 23 and 29 (including 23 and 29) of them live in...
67% of all Americans live in cities with population greater than 100,000 people. If 35 Americans...
67% of all Americans live in cities with population greater than 100,000 people. If 35 Americans are randomly selected, find the probability that a. Exactly 21 of them live in cities with population greater than 100,000 people.   b. At most 22 of them live in cities with population greater than 100,000 people. c. At least 24 of them live in cities with population greater than 100,000 people.   d. Between 17 and 22 (including 17 and 22) of them live in...
Suppose it is known that 40% of households own some sort of gaming console. If 15...
Suppose it is known that 40% of households own some sort of gaming console. If 15 people are selected at random, what is the probability that exactly 6 individuals in the sample own some sort of gaming console? a. 0.0041 b. 0.2066 c. 0.5000 d. 0.4000 e. 0.6098
A population is known to have a mean of 10 and a standard deviation of 1.1....
A population is known to have a mean of 10 and a standard deviation of 1.1. A sample of size 32 is randomly selected from the population. a. What is the probability that the sample mean is less than 9.9? b. What percent of the population is greater than 10.2? c. What’s the probability that the sample mean is greater than 10.5?
70% of all Americans live in cities with population greater than 100,000 people. If 34 Americans...
70% of all Americans live in cities with population greater than 100,000 people. If 34 Americans are randomly selected, find the following probabilities. Round your answers to 4 decimal places. a. Exactly 24 of them live in cities with population greater than 100,000 people. b. At most 23 of them live in cities with population greater than 100,000 people. c. At least 23 of them live in cities with population greater than 100,000 people. d. Between 20 and 27 (including...
According to a study conducted by an​ organization, the proportion of Americans who were afraid to...
According to a study conducted by an​ organization, the proportion of Americans who were afraid to fly in 2006 was 0.10. A random sample of 1,300 Americans results in 143 indicating that they are afraid to fly. Explain why this is not necessarily evidence that the proportion of Americans who are afraid to fly has increased. A. This is not necessarily evidence that the proportion of Americans who are afraid to fly has increased above 0.10 because the probability of...
Suppose the lengths of pregnancies of a certain animal are approximately normally distributed with mean ?...
Suppose the lengths of pregnancies of a certain animal are approximately normally distributed with mean ? = 240 days and ? = 18 days. a. What is the probability that a randomly selected pregnancy lasts less than 233 days? b. Suppose a random sample of 17 pregnancies is obtained. Describe the mean and standard deviation of the distribution of the sample mean length of pregnancies. c. What is the probability that a random sample of 17 pregnancies has a mean...
7. In the US, 40% of the population)n have brown eyes. If 14 people are randomly...
7. In the US, 40% of the population)n have brown eyes. If 14 people are randomly selected then a) find the average number and standard deviation of people with brown eyes b) P(at least 12 of them will have brown eyes) c) P(exactly 7 will have brown eyes) d)P(less then 4 or more than 10 of them will have brown eyes)
According to a study conducted by an​ organization, the proportion of Americans who were afraid to...
According to a study conducted by an​ organization, the proportion of Americans who were afraid to fly in 2006 was 0.10. A random sample of 1 comma 1001,100 Americans results in 9999 indicating that they are afraid to fly. Explain why this is not necessarily evidence that the proportion of Americans who are afraid to fly has decreaseddecreased. Select the correct choice below​ and, if​ necessary, fill in the answer box to complete your choice. A.This is not necessarily evidence...
ADVERTISEMENT
Need Online Homework Help?

Get Answers For Free
Most questions answered within 1 hours.

Ask a Question
ADVERTISEMENT