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Setler [38]
2 years ago
10

Juliet conducted a survey to find the favorite type of book of the students at her school. She asked 20 students from her class

what their favorite type of book is. Juliet concludes that short stories is the favorite type of book of the students in her school because 80% of the students in her class like short stories. Use at least two sentences to explain why Juliet's sample may not be valid. Make sure to use facts to support your answer.
Mathematics
1 answer:
pantera1 [17]2 years ago
3 0
The reason is because she didn't survey the school, but only surveyed her class, and to add to that It didn't say it was a random selection of students.

Juliet concludes that short stories is the favorite type of book of the students in her school because 80% of the students in her class like short stories.

That is inaccurate, she is assuming, that just because the students in her class chose short stories, she assumes the rest of the students will chose it.

Hope this helps! xx
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Shawna has $750 in the bank.she deposits $37.50 each week.Ruben has $850 in the bank.He deposits his paycheck of $102.75 every M
erastova [34]

Answer:

Step-by-step explanation:

Answer: it would take 20 weeks before the amount in both accounts would be the same.

Step-by-step explanation:

Let x represent the number of weeks that it will take either Ruben and Shawna to have the same amount of money in their account.

Let y represent the total amount that would be in Shawna's account after x weeks

Let z represent the total amount that would be in Ruben's account after x weeks

Shawna has $750 in the bank. She deposits $37.50 each week. This means that the total amount after x weeks would be

y = 37.5x + 750

Ruben has $850 in the bank. He deposits his paycheck of $102.75 every Monday,and he spends about $70.25 each week.. This means that the total amount after x weeks would be

z = 850 + 102.75x - 70.25x

z = 850 + 32.5x

To determine the number of weeks before the amount in both accounts will becomes the same, we would equate y to z. It becomes

37.5x + 750= 850 + 32.5x

37.5x - 32.5x = 850 - 750

5x = 100

x = 100/5 = 20

8 0
2 years ago
The heat evolved in calories per gram of a cement mixture is approximately normally distributed. The mean is thought to be 100,
Gre4nikov [31]

Answer:

A.the type 1 error probability is \mathbf{\alpha = 0.0244 }

B. β  = 0.0122

C. β  = 0.0000

Step-by-step explanation:

Given that:

Mean = 100

standard deviation = 2

sample size = 9

The null and the alternative hypothesis can be computed as follows:

\mathtt{H_o: \mu = 100}

\mathtt{H_1: \mu \neq 100}

A. If the acceptance region is defined as 98.5 <  \overline x >  101.5 , find the type I error probability \alpha .

Assuming the critical region lies within \overline x < 98.5 or \overline x > 101.5, for a type 1 error to take place, then the sample average x will be within the critical region when the true mean heat evolved is \mu = 100

∴

\mathtt{\alpha = P( type  \ 1  \ error ) = P( reject \  H_o)}

\mathtt{\alpha = P( \overline x < 98.5 ) + P( \overline x > 101.5  )}

when  \mu = 100

\mathtt{\alpha = P \begin {pmatrix} \dfrac{\overline X - \mu}{\dfrac{\sigma}{\sqrt{n}}} < \dfrac{\overline 98.5 - 100}{\dfrac{2}{\sqrt{9}}} \end {pmatrix} + \begin {pmatrix}P(\dfrac{\overline X - \mu}{\dfrac{\sigma}{\sqrt{n}}}  > \dfrac{101.5 - 100}{\dfrac{2}{\sqrt{9}}} \end {pmatrix} }

\mathtt{\alpha = P ( Z < \dfrac{-1.5}{\dfrac{2}{3}} ) + P(Z  > \dfrac{1.5}{\dfrac{2}{3}}) }

\mathtt{\alpha = P ( Z  2.25) }

\mathtt{\alpha = P ( Z

From the standard normal distribution tables

\mathtt{\alpha = 0.0122+( 1-  0.9878) })

\mathtt{\alpha = 0.0122+( 0.0122) })

\mathbf{\alpha = 0.0244 }

Thus, the type 1 error probability is \mathbf{\alpha = 0.0244 }

B. Find beta for the case where the true mean heat evolved is 103.

The probability of type II error is represented by β. Type II error implies that we fail to reject null hypothesis \mathtt{H_o}

Thus;

β = P( type II error) - P( fail to reject \mathtt{H_o} )

∴

\mathtt{\beta = P(98.5 \leq \overline x \leq  101.5)           }

Given that \mu = 103

\mathtt{\beta = P( \dfrac{98.5 -103}{\dfrac{2}{\sqrt{9}}} \leq \dfrac{\overline X - \mu}{\dfrac{\sigma}{n}} \leq \dfrac{101.5-103}{\dfrac{2}{\sqrt{9}}}) }

\mathtt{\beta = P( \dfrac{-4.5}{\dfrac{2}{3}} \leq Z \leq \dfrac{-1.5}{\dfrac{2}{3}}) }

\mathtt{\beta = P(-6.75 \leq Z \leq -2.25) }

\mathtt{\beta = P(z< -2.25) - P(z < -6.75 )}

From standard normal distribution table

β  = 0.0122 - 0.0000

β  = 0.0122

C. Find beta for the case where the true mean heat evolved is 105. This value of beta is smaller than the one found in part (b) above. Why?

\mathtt{\beta = P(98.5 \leq \overline x \leq  101.5)           }

Given that \mu = 105

\mathtt{\beta = P( \dfrac{98.5 -105}{\dfrac{2}{\sqrt{9}}} \leq \dfrac{\overline X - \mu}{\dfrac{\sigma}{n}} \leq \dfrac{101.5-105}{\dfrac{2}{\sqrt{9}}}) }

\mathtt{\beta = P( \dfrac{-6.5}{\dfrac{2}{3}} \leq Z \leq \dfrac{-3.5}{\dfrac{2}{3}}) }

\mathtt{\beta = P(-9.75 \leq Z \leq -5.25) }

\mathtt{\beta = P(z< -5.25) - P(z < -9.75 )}

From standard normal distribution table

β  = 0.0000 - 0.0000

β  = 0.0000

The reason why the value of beta is smaller here is that since the difference between the value for the true mean and the hypothesized value increases, the probability of type II error decreases.

8 0
2 years ago
Label the place value 12,354.897
Angelina_Jolie [31]
From left to right

Ten thousands, thousands, hundreds, tens, ones, tenths, hundreths, thousandths,
6 0
2 years ago
Read 2 more answers
Estimate the sum of 299 and 388
myrzilka [38]
The estimate of 299 is 300. The estimate of 388 is 400. So, 300 + 400 = 700
8 0
2 years ago
Read 2 more answers
In circle M, diameters JL and HK each measure 16 centimeters.
sashaice [31]

Answer:

3.5 cm

Step-by-step explanation:

Length of an arc is a "part" of the circumference of a circle.

The circumference is the perimeter of the circle. Formula is:

C=\pi d

Where

C is circumference

d is diameter

Given diameter is 16, the circumference would be:

C=\pi (16)\\C=16\pi\\C=50.27

Now, the arc is 25 degrees, which is 25/360 th of the circle's circumference [recall, there is 360 degrees in whole circle].

So, we multiply the circumference we got by (25/360) to get our answer:

\frac{25}{360}*50.27=3.5

Minor Arc JH = 3.5 cm

7 0
2 years ago
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