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3 years ago

Please help with c and i. and ii.

Mathematics

1 answer:

GaryK [48]3 years ago

8 0

Take however many boys/girls there are and divide it by how many sports there are... so 250/3= 83 boys per sport and 80 girls per sport.

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Solve the system of equations

IceJOKER [234]

<h3>Answer:</h3>

c) there are infinitely many solutions

<h3>Explanation:</h3>

Add x to the <em>first equation</em> to put it in standard form:

... x + y = 3

Divide the <em>second equation</em> by the common factor of all terms, 2, to put it in standard form:

... x + y = 3

These two equations describe the same line. Every point on the line is a solution to both equations, so there are infinitely many solutions. (We say these equations are "dependent.")

3 0

3 years ago

Plz ANWSER no one else will amwser this

RoseWind [281]

Answer:

1. 80.5

2. 432

3. 310.5

4. 26

Step-by-step explanation:

6 0

3 years ago

The authors of a paper describe an experiment to evaluate the effect of using a cell phone on reaction time. Subjects were asked

Serggg [28]

Answer:

a) The 99% confidence interval would be given by (24.409;24.979)

b) n=464

Step-by-step explanation:

A confidence interval is "a range of values that’s likely to include a population value with a certain degree of confidence. It is often expressed a % whereby a population means lies between an upper and lower interval".

The margin of error is the range of values below and above the sample statistic in a confidence interval.

Normal distribution, is a "probability distribution that is symmetric about the mean, showing that data near the mean are more frequent in occurrence than data far from the mean".

Part a

The confidence interval for the mean is given by the following formula:

$\bar X \pm t_{\alpha/2}\frac{s}{\sqrt{n}}$ (1)

In order to calculate the critical value $t_{\alpha/2}$ we need to find first the degrees of freedom, given by:

$df=n-1=47-1=46$

Since the Confidence is 0.95 or 95%, the value of $\alpha=0.05$ and $\alpha/2 =0.025$ , and we can use excel, a calculator or a table to find the critical value. The excel command would be: "=-T.INV(0.025,46)".And we see that $t_{\alpha/2}=2.01$

Now we have everything in order to replace into formula (1):

$525-2.01\frac{75}{\sqrt{47}}=503.01$

$525+2.01\frac{75}{\sqrt{47}}=546.99$

So on this case the 95% confidence interval would be given by (503.01;546.99)

Part b

The margin of error is given by this formula:

$ME=t_{\alpha/2}\frac{s}{\sqrt{n}}$ (1)

And on this case we have that ME =7 msec, we are interested in order to find the value of n, if we solve n from equation (1) we got:

$n=(\frac{t_{\alpha/2} s}{ME})^2$ (2)

The critical value for 95% of confidence interval is provided, $t_{\alpha/2}=2.01$ from part a, replacing into formula (2) we got:

$n=(\frac{2.01(75)}{7})^2 =463.79 \approx 464$

So the answer for this case would be n=464 rounded up to the nearest integer

8 0

3 years ago

The probability of event A is x, and the probability of event B is y. If the two events are independent, which of these conditio

zzz [600]

If two events are independent, then

$Pr(A\cap B)=Pr(A)\cdot Pr(B)$ .

Use formulas for conditional probabilities:

$Pr(A|B)=\dfrac{Pr(A\cap B)}{Pr(B)},\\ \\ Pr(B|A)=\dfrac{Pr(A\cap B)}{Pr(A)}$ .

For independent events these formulas will be:

$Pr(A|B)=\dfrac{Pr(A\cap B)}{Pr(B)}=\dfrac{Pr(A)\cdot Pr(B)}{Pr(B)}=Pr(A),\\ \\ Pr(B|A)=\dfrac{Pr(A\cap B)}{Pr(A)}=\dfrac{Pr(A)\cdot Pr(B)}{Pr(A)}=Pr(B)$ .