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arlik [135]
3 years ago
10

Students were surveyed about their favorite colors 1/4 of the students preferred read 1/8 of the students preferred blue and 3/5

of the remaining students were for green if 15 students prefer green how many students were surveyed
Mathematics
1 answer:
Elanso [62]3 years ago
5 0

Answer: the number of students that were surveyed is 40

Step-by-step explanation:

Let x = total number of students that were surveyed about their favorite colors

1/4 of the students preferred red.

This means that the number of students that preferred red is 1/4 × x = x/4

1/8 of the students preferred blue.

This means that the number of students that preferred blue is 1/8 × x = x/8

The remaining number of students will be the total number of students - the sum of the number of students that preferred red and the number of students that preferred blue. It becomes

x - (x/4 + x/8) = x - 3x/8 = 5x/8

3/5 of the remaining students were for green. This means that the number of students that preferred green is 3/5 × 5x/8 = 3x/8

if 15 students prefer green, then

3x/8 = 15

3x = 120

x = 120/3 = 40 students

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According to a recent Census Bureau report, 12.7% of Americans live below the poverty level. Suppose you plan to sample at rando
larisa [96]

Answer:

a) P(X=10)=(100C10)(0.127)^{10} (1-0.127)^{100-10}=0.0928

b) P(X \leq 10) = 0.2614

c) (1-0.127)^7 (0.127) =0.0491

Step-by-step explanation:

Previous concepts

The binomial distribution is a "DISCRETE probability distribution that summarizes the probability that a value will take one of two independent values under a given set of parameters. The assumptions for the binomial distribution are that there is only one outcome for each trial, each trial has the same probability of success, and each trial is mutually exclusive, or independent of each other".

Solution to the problem

Let X the random variable of interest, on this case we now that:

X \sim Binom(n=100, p=0.127)

The probability mass function for the Binomial distribution is given as:

P(X)=(nCx)(p)^x (1-p)^{n-x}

Where (nCx) means combinatory and it's given by this formula:

nCx=\frac{n!}{(n-x)! x!}

a. What is the probability that you count exactly 10 in poverty?

For this case we want this probability P(X=10)

P(X=10)=(100C10)(0.127)^{10} (1-0.127)^{100-10}=0.0928

b. What is the probability that you count 10 or less in poverty?  .2614

For this case we want this probability P(X=\leq10)

P(X\leq10)=P(X=1)+P(X=2)+P(X=3)+P(X=4)+P(X=5)+P(X=6)+P(X=7)+P(X=8)+P(X=9)+P(X=10)

And we can find the individual probabilities like this:

P(X=0)=(100C0)(0.127)^{0} (1-0.127)^{100-0}=1.263x10^{-6}

P(X=1)=(100C1)(0.127)^{1} (1-0.127)^{100-1}=1.837x10^{-5}

P(X=2)=(100C2)(0.127)^{2} (1-0.127)^{100-2}=0.000132

P(X=3)=(100C3)(0.127)^{3} (1-0.127)^{100-3}=0.000629

P(X=4)=(100C4)(0.127)^{4} (1-0.127)^{100-4}=0.00222

P(X=5)=(100C5)(0.127)^{5} (1-0.127)^{100-5}=0.00620

P(X=6)=(100C6)(0.127)^{6} (1-0.127)^{100-6}=0.0143

P(X=7)=(100C7)(0.127)^{7} (1-0.127)^{100-7}=0.0279

P(X=8)=(100C8)(0.127)^{8} (1-0.127)^{100-8}=0.0471

P(X=9)=(100C9)(0.127)^{9} (1-0.127)^{100-9}=0.0701

P(X=10)=(100C10)(0.127)^{10} (1-0.127)^{100-10}=0.0928

And then repplacing we got:

P(X \leq 10) = 0.2614

c. What is the probability that you start taking the random sample and you find the first person in poverty on the 8th person selected?  .0491

For this case we need after 7 people , 1 in poverty so we can find this probability like this:

(1-0.127)^7 (0.127) =0.0491

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432311<br> Extended form
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Step-by-step explanation:

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Answer:

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Step-by-step explanation:

II started by multiplying 19*15% and then kept going from 15 to 20 to 25  then to 30 and it was right

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Step-by-step explanation:

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