Help! I will give brainliest!

A university found that 20% of its students withdraw without completing the introductory statistics course. Assume that 20 stude

EleoNora [17]

Answer:

a) $P(X \leq 2)= P(X=0)+P(X=1)+P(X=2)$

And we can use the probability mass function and we got:

$P(X=0)=(20C0)(0.2)^0 (1-0.2)^{20-0}=0.0115$

$P(X=1)=(20C1)(0.2)^1 (1-0.2)^{20-1}=0.0576$

$P(X=2)=(20C2)(0.2)^2 (1-0.2)^{20-2}=0.1369$

And adding we got:

$P(X \leq 2)=0.0115+0.0576+0.1369 = 0.2061$

b) $P(X=4)=(20C4)(0.2)^4 (1-0.2)^{20-4}=0.2182$

c) $P(X>3) = 1-P(X \leq 3) = 1- [P(X=0)+P(X=1)+P(X=2)+P(X=3)]$

$P(X=0)=(20C0)(0.2)^0 (1-0.2)^{20-0}=0.0115$

$P(X=1)=(20C1)(0.2)^1 (1-0.2)^{20-1}=0.0576$

$P(X=2)=(20C2)(0.2)^2 (1-0.2)^{20-2}=0.1369$

$P(X=3)=(20C3)(0.2)^3 (1-0.2)^{20-3}=0.2054$

And replacing we got:

$P(X>3) = 1-[0.0115+0.0576+0.1369+0.2054]= 1-0.4114= 0.5886$

d) $E(X) = 20*0.2= 4$

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:

$X \sim Binom(n=20, p=0.2)$

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:

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

Part a

We want this probability:

$P(X \leq 2)= P(X=0)+P(X=1)+P(X=2)$

And we can use the probability mass function and we got:

$P(X=0)=(20C0)(0.2)^0 (1-0.2)^{20-0}=0.0115$

$P(X=1)=(20C1)(0.2)^1 (1-0.2)^{20-1}=0.0576$

$P(X=2)=(20C2)(0.2)^2 (1-0.2)^{20-2}=0.1369$

And adding we got:

$P(X \leq 2)=0.0115+0.0576+0.1369 = 0.2061$

Part b

We want this probability:

$P(X=4)$

And using the probability mass function we got:

$P(X=4)=(20C4)(0.2)^4 (1-0.2)^{20-4}=0.2182$

Part c

We want this probability:

$P(X>3)$

We can use the complement rule and we got:

$P(X>3) = 1-P(X \leq 3) = 1- [P(X=0)+P(X=1)+P(X=2)+P(X=3)]$

$P(X=0)=(20C0)(0.2)^0 (1-0.2)^{20-0}=0.0115$

$P(X=1)=(20C1)(0.2)^1 (1-0.2)^{20-1}=0.0576$

$P(X=2)=(20C2)(0.2)^2 (1-0.2)^{20-2}=0.1369$

$P(X=3)=(20C3)(0.2)^3 (1-0.2)^{20-3}=0.2054$

And replacing we got:

$P(X>3) = 1-[0.0115+0.0576+0.1369+0.2054]= 1-0.4114= 0.5886$

Part d

The expected value is given by:

$E(X) = np$

And replacing we got:

$E(X) = 20*0.2= 4$

3 0

2 years ago

A soft drink manufacturer wishes to know how many soft drinks adults drink each week. They want to construct a 85% confidence in

andreev551 [17]

Answer: 547

Step-by-step explanation: The margin of error formulae is given below as

Margin of error = critical value ×(σ/√n)

Where σ = standard deviation and n is the sample size.

From our question, margin of error = 0.08

Variance is 1.691,

hence σ = √variance = √1.691

= 1.3.

We will be using a z test for our critical value this is because a soft drink manufacturer will always produce drinks more than 30 in numbers.

The critical value for a 85% confidence interval is 1.44.

Hence critical value is 1.44.

By substituting the parameters, we have that

0.08 = 1.44 × 1.3/ √n

0.08 = 1.873/ √n

By cross multiplying

0.08 × √n = 1.873

√n = 1.873/ 0.08

√n = 23.41

n = (23.41)²

n = 547.

7 0

2 years ago

From an aeroplane vertically above a straight horizontal plane, the angles of depression of two consecutive kilometres stones on

Airida [17]

You have to build the triangles.

They are such that:
h is the common height
x is the horizontal distance from the plane to one stone
Beta is the angle between x and the hypotenuse

Then in this triangle: tan(beta) = h / x ......(1)

1 - x is the horizontal distance from the plane to the other stone
alfa is the angle between 1 - x and h

Then, in this triangle: tan (alfa) = h / [1 -x ] ...... (2)

from (1) , x = h / tan(beta)

Substitute this value in (2)

tan(alfa) = h / { [ 1 - h / tan(beta)] } =>

{ [ 1 - h / tan(beta) ] } tan(alfa) = h

[tan(beta) - h] tan(alfa) = h*tan(beta)

tan(beta)tan(alfa) - htan(alfa) = htan(beta)

h [tan(alfa) + tan(beta) ] = tan(beta) tan (alfa)

h = tan(beta)*tan(alfa) / (t an(alfa) + tan(beta) )

4 0

3 years ago

1) Which of the following does not show the Commutative Property of Addition ?

Luda [366]

Answer:

I think it would be c.ab=ba but im not 100% sure

Step-by-step explanation:

4 0

2 years ago

Slope for (1,5) (3,4)

frez [133]

Answer:

-1,2

Step-by-step explanation:

4-5=-1

3-1=2

y2-y1

x2-x1

8 0

2 years ago