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Alex Ar [27]
2 years ago
10

If A and B are independent events with P(A) = .5 and P(B) = .2, find the following:a) P(A U B)b) P(A^c ? B^c)c) P(A^c U B^c)**No

te A^c or B^c refers to A complement or B complement**
Mathematics
1 answer:
Effectus [21]2 years ago
4 0

If A and B are independent, then P(A\cap B)=P(A)P(B).

a.

P(A\cup B)=P(A)+P(B)-P(A\cap B)=P(A)+P(B)-P(A)P(B)

P(A\cup B)=0.5+0.2-0.5\cdot0.2

\boxed{P(A\cup B)=0.6}

b. I'm guessing the ? is supposed to stand for intersection. We can use DeMorgan's law for complements here:

P(A^c\cap B^c)=P(A\cup B)^c=1-P(A\cup B)

P(A^c\cap B^c)=1-0.6

\boxed{P(A^c\cap B^c)=0.4}

c. DeMorgan's law can be used here too:

P(A^c\cup B^c)=P(A\cap B)^c=1-P(A\cap B)=1-P(A)P(B)

P(A^c\cup B^c)=1-0.5\cdot0.2

\boxed{P(A^c\cup B^c)=0.9}

You might be interested in
A researcher used a sample of n = 60 individuals to determine whether there are any preferences among six brands of pizza. Each
Blizzard [7]

Answer:

1) χ² ≥ 11.07

2) Goodness of fit test, df: χ²_{3}

Independence test, df: χ²_{1}

The goodness of fit test has more degrees of freedom than the independence test.

3) e_{females.} = 80

4) H₀: P_{ij}= P_{i.} * P_{.j} ∀ i= 1, 2, ..., r and j= 1, 2, ..., c

5) χ²_{6}

Step-by-step explanation:

Hello!

1)

The researcher took a sample of n=60 people and made them taste proof samples of six different brands of pizza and choose their favorite brand, their choose was recorded. So the study variable is the following:

X: favorite pizza brand, categorized in brand 1, brand 2, brand 3, brand 4, brand 5 and brand 6.

The Chi-square goodness of fit test is done with the following statistic:

χ²= ∑\frac{(O_i-E_i)^2}{E_i} ≈χ²_{k-1}

Where k represents the number of categories of the study variable. In this example k= 6.

Remember, the rejection region for the Chi-square tests of "goodnedd of fit", "independence", and "homogeneity" is allways one-tailed to the right. So you will only have one critical value.

χ²_{k-1; 1 - \alpha }

χ²_{6-1; 1 - 0.05 }

χ²_{5; 0.95 } = 11.070

This means thar the rejection region is χ² ≥ 11.07

If the Chi-Square statistic is equal or greather than 11.07, then you reject the null hypothesis.

2)

The statistic for the goodness of fit is:

χ²= ∑\frac{(O_i-E_i)^2}{E_i} ≈χ²_{k-1}

Degrees of freedom: χ²_{k-1}

In the example: k= 4 (the variable has 4 categories)

χ²_{4-1} = χ²_{3}

The statistic for the independence test is:

χ²= ∑∑\frac{(O_ij-E_ij)^2}{E_ij} ≈χ²_{(r-1)(c-1)} ∀ i= 1, 2, ..., r & j= 1, 2, ..., c

If the information is in a contingency table

r= represents the total of rows

c= represents the total of columns

In the example: c= 2 and r= 2

Degrees of freedom: χ²_{(r-1)(c-1)}

χ²_{(2-1)(2-1)} = χ²_{1}

The goodness of fit test has more degrees of freedom than the independence test.

3)

To calculate the expected frecuencies for the independence test you have to use the following formula.

e_{ij} = n * P_i. * P_.j = n * \frac{o_i.}{n} * \frac{o_.j}{n}

Where o_i. represents the total observations of the i-row, o_.j represents the total of observations of the j-column and n is the sample size.

Now, this is for the expected frequencies in the body of the contingency table, this means the observed and expected frequencies for each crossing of categories is not the same.

On the other hand, you would have the totals of each category and population in the margins of the table (subtotals), this is the same when looking at the observed frequencies and the expected frequencies. Wich means that the expected frequency for the total of a population is the same as the observed frequency of said population. A quick method to check if your calculations of the expected frequencies for one category/population are correct is to add them, if the sum results in the subtotal of that category/population, it means that you have calculated the expected frequencies correctly.

The expected frequency for the total of females is 80

Using the formula:

(If the females are in a row) e_{females.} = 100 * \frac{80}{100} * \frac{0}{100}

e_{females.} = 80

4)

There are two ways of writing down a null hypothesis for the independence test:

Way 1: using colloquial language

H₀: The variables X and Y are independent

Way 2: Symbolically

H₀: P_{ij}= P_{i.} * P_{.j} ∀ i= 1, 2, ..., r and j= 1, 2, ..., c

This type of hypothesis follows from the definition of independent events, where if we have events A and B independent of each other, the probability of A and B is equal to the product of the probability of A and the probability of B, symbolically: P(A∩B) = P(A) * P(B)

5)

In this example, you have an independence test for two variables.

Variable 1, has 3 categories

Variable 2, has 4 categories

To follow the notation, let's say that variable 1 is in the rows and variable 2 is in the columns of the contingency table.

The statistic for this test is:

χ²= ∑∑\frac{(O_ij-E_ij)^2}{E_ij} ≈χ²_{(r-1)(c-1)} ∀ i= 1, 2, ..., r & j= 1, 2, ..., c

In the example: c= 3 and r= 4

Degrees of freedom: χ²_{(r-1)(c-1)}

χ²_{(3-1)(4-1)} = χ²_{6}

I hope you have a SUPER day!

4 0
3 years ago
Please help I’ll give brainliest
lesantik [10]

Answer: $108199

Step-by-step explanation:

Step 1) Find the deposit cost

35/100 × 89540 = 31339

Step 2) Find the total cost of the monthly payments

2135 × 36 = 76860

Step 3) Find the final cost

31339 + 76860 = $108199

4 0
3 years ago
write the following inequality in slope-intercept form. –6x 2y ≤ 42 a. y ≥ 3x 21 b. y ≤ 3x – 21 c. y ≥ 3x – 21 d. y ≤ 3x 21
borishaifa [10]
-6x + 2y =< 42
2y =< 6x + 42
y =< 3x + 21
4 0
3 years ago
Read 2 more answers
Which system of inequalities is represented by the graph?
timofeeve [1]

Answer:

The system of inequalities " x + 2 y ≤ 5 and 3 x + y ≤ 4 " is represented by the graph ⇒ D

Step-by-step explanation:

To find the answer let us find the equation of each line

Blue line:

∵ The line passes through points (5 , 0) and (0 , 2.5)

- Find the slope of the line

∵ m = Δy/Δx

∴ \frac{0-2.5}{5-0}=\frac{-2.5}{5}

∴ m = -0.5

- The form of the equation is y = m x  + b, where b is the

   y-intercept (value y at x = 0)

∵ y = 2.5 at x = 0

∴ b = 2.5

- Write the equation of the line

∴ y = - 0.5 x + 2.5

- Multiply both sides by 2

∴ The equation of the blue line is 2 y = - x + 5

- The shading is under the line and the line is solid, that means

  2 y is less than or equal - x + 5

∴ The inequality of the blue line is 2 y ≤ - x + 5

Red line:

∵ The line passes through points (3 , -5) and (0 , 4)

- Find the slope of the line

∴ m=\frac{-5-4}{3-0}=\frac{-9}{3}

∴ m = -3

∵ y = 4 at x = 0

∴ b = 4

- Write the equation of the line

∴ y =  -3 x + 4

∴ The equation of the red line is y = -3 x + 4

- The shading is below the line and the line is solid, that means

  y is less than or equal -3 x + 4

∴ The inequality of the red line is y ≤ -3 x + 4

Let us find which answer is the same with this system of inequalities

∵ 2 y ≤ - x + 5

- Add x to both sides

∴ x + 2 y ≤ 5 ⇒ same as the first inequality of answer D

∵ y ≤ -3 x + 4

- Add 3 x to both sides

∴ 3 x + y ≤ 4 ⇒ same as the second inequality of answer D

The system of inequalities " x + 2 y ≤ 5 and 3 x + y ≤ 4" is represented by the graph

4 0
3 years ago
Two radio stations are playing this week's #1 hit song. One radio station plays the song every 18 minutes. The other radio stati
V125BC [204]

The next time the stations will play the song at the same time would be at 4:12 P.M. because 18×4=72 and 24×3=72 and this is the first number that they share.

3 0
2 years ago
Read 2 more answers
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