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3 years ago

Quick plz help asap marking brainliest for first answer as long as you include steps !!!

Mathematics

1 answer:

Akimi4 [234]3 years ago

7 0

Answer:

a=2.48

c=9.52

Step-by-step explanation:

a+c=12

4a+7.5c=72.5 Given

a+c=12

-4a-7.5c=-72.5 multiply the equation by negative 1

-3a-6.5c=-60.5 simplify

-3a=-60.5+6.5c add 6.5c to both sides

a=-20.17+2.17c divide it by 3

now you would take that equation and plug it into an equation you already have since you have something to plug in for a, the easiest one to do is a+c=12

(-20.17+2.17c)+c=12 plug in the equation

-20.17+3.17c=12 simplify by solving for c

3.17c=30.17 add 20.17 to both sides

c=9.52 divide both sides by 3.17

now since you have found c, you can plug it in to you equation to solve for a now (use the ones from the second step). I am using the equation a+c=12.

a+9.52=12 plug in the variable and solve for a

a=2.48 subtract 9.52 to both sides

a=2.48

c=9.52

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Using the normal approximation to the binomial, it is found that:

The mean of X is of 52 samples.
The standard deviation of X is of 4.2661 samples.
0.0017 = 0.17% probability that less than half without any traces of pesticide.

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Binomial probability distribution

Probability of exactly x successes on n repeated trials, with p probability.

Can be approximated to a normal distribution, with mean given by:

$E(X) = np$

And standard deviation of:

$\sqrt{V(X)} = \sqrt{np(1-p)}$

Normal probability distribution

Z-score formula is used, which, in a set with mean $\mu$ and standard deviation $\sigma$ , the z-score of a measure X is given by:

$Z = \frac{X - \mu}{\sigma}$

Each z-score has an associated p-value, which measures the percentile of measure X.

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65% of samples had no pesticide, thus $p = 0.65$
80 samples, thus $n = 80$

The mean of X is of:

$E(X) = np = 0.65(80) = 52$

The standard deviation of X is of:

$\sqrt{V(X)} = \sqrt{np(1-p)} = \sqrt{80(0.65)(0.35)} = 4.2661$

Using the approximation and continuity correction, the probability is $P(X < 40 - 0.5) = P(X < 39.5)$ , which is the p-value of Z when X = 39.5. Thus:

$Z = \frac{X - \mu}{\sigma}$

$Z = \frac{39.5 - 52}{4.2661}$

$Z = -2.93$

$Z = -2.93$ has a p-value of 0.0017, thus:

0.0017 = 0.17% probability that less than half without any traces of pesticide.

A similar problem is given at brainly.com/question/24261244

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2 years ago

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Answer:

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Step-by-step explanation:

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3 years ago

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1500 members have a contributor membership.

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Step-by-step explanation:

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From the graph shown,

7.5% of the members have a contributor membership.

To find the number of members who have contributor membership :

⇒ 7.5% of 20,000

⇒ (7.5/100) × 20,000

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⇒ 1500 members.

Therefore, 1500 members have a contributor membership.

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3 years ago

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3 years ago

With a height of 68 in, Nelson was the shortest president of a particular club in the past century. The club presidents of the

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Answer:

a. The positive difference between Nelson's height and the population mean is: $\\ \lvert 68-70.7 \rvert = \lvert 70.7-68 \rvert\;in = 2.7\;in$ .

b. The difference found in part (a) is 1.174 standard deviations from the mean (without taking into account if the height is above or below the mean).

c. Nelson's z-score: $\\ z = -1.1739 \approx -1.174$ (Nelson's height is below the population's mean 1.174 standard deviations units).

d. Nelson's height is usual since $\\ -2 < -1.174 < 2$ .

Step-by-step explanation:

The key concept to answer this question is the z-score. A z-score "tells us" the distance from the population's mean of a raw score in standard deviation units. A positive value for a z-score indicates that the raw score is above the population mean, whereas a negative value tells us that the raw score is below the population mean. The formula to obtain this z-score is as follows:

$\\ z = \frac{x - \mu}{\sigma}$ [1]

Where

$\\ z$ is the z-score.

$\\ \mu$ is the population mean.

$\\ \sigma$ is the population standard deviation.

From the question, we have that:

Nelson's height is 68 in. In this case, the raw score is 68 in $\\ x = 68$ in.
$\\ \mu = 70.7$ in.
$\\ \sigma = 2.3$ in.

With all this information, we are ready to answer the next questions:

a. What is the positive difference between Nelson's height and the mean?

The positive difference between Nelson's height and the population mean is (taking the absolute value for this difference):

$\\ \lvert 68-70.7 \rvert = \lvert 70.7-68 \rvert\;in = 2.7\;in$ .

That is, the positive difference is 2.7 in.

b. How many standard deviations is that [the difference found in part (a)]?

To find how many standard deviations is that, we need to divide that difference by the population standard deviation. That is:

$\\ \frac{2.7\;in}{2.3\;in} \approx 1.1739 \approx 1.174$

In words, the difference found in part (a) is 1.174 standard deviations from the mean. Notice that we are not taking into account here if the raw score, x, is below or above the mean.

c. Convert Nelson's height to a z score.

Using formula [1], we have

$\\ z = \frac{x - \mu}{\sigma}$

$\\ z = \frac{68\;in - 70.7\;in}{2.3\;in}$

$\\ z = \frac{-2.7\;in}{2.3\;in}$

$\\ z = -1.1739 \approx -1.174$

This z-score "tells us" that Nelson's height is 1.174 standard deviations below the population mean (notice the negative symbol in the above result), i.e., Nelson's height is below the mean for heights in the club presidents of the past century 1.174 standard deviations units.

d. If we consider "usual" heights to be those that convert to z scores between minus2 and 2, is Nelson's height usual or unusual?

Carefully looking at Nelson's height, we notice that it is between those z-scores, because:

$\\ -2 < z_{Nelson} < 2$

$\\ -2 < -1.174 < 2$

Then, Nelson's height is usual according to that statement.

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3 years ago