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Brilliant_brown [7]

3 years ago

9

Mr. Sharon can paper a room in 3hrs. His assistant needs 5hrs. If Mr. Sharon works 1hr and then his assistant completes the job

alone, how long will it take the assistant to finish the job?

1 answer:

stealth61 [152]3 years ago

6 0

4 hours? Sorry if it's wrong

hope I helped!!!

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Silicon wafers are scored and then broken into the many small microchips that will he mounted into circuits. Two breaking method

antoniya [11.8K]

Answer:

a

The estimate is $- 0.0265\le K \le 0.0465$

b

Method B this is because the faulty breaks are less

Step-by-step explanation:

The number of microchips broken in method A is $n_1 = 400$

The number of faulty breaks of method A is $X_1 = 32$

The number of microchips broken in method B is $n_2 = 400$

The number of faulty breaks of method A is $X_2 = 32$

The proportion of the faulty breaks to the total breaks in method A is

$p_1 = \frac{32}{400}$

$p_1 = 0.08$

The proportion of the faulty to the total breaks in method B is

$p_2 = \frac{28}{400}$

$p_2 = 0.07$

For this estimation the standard error is

$SE = \sqrt{ \frac{p_1 (1 - p_1)}{n_1} + \frac{p_2 (1- p_2 )}{n_2} } }$

substituting values

$SE = \sqrt{ \frac{0.08 (1 - 0.08)}{400} + \frac{0.07 (1- 0.07 )}{400} } }$

$SE = 0.0186$

The z-values of confidence coefficient of 0.95 from the z-table is

$z_{0.95} = 1.96$

The difference between proportions of improperly broken microchips for the two breaking methods is mathematically represented as

$K = [p_1 - p_2 ] \pm z_{0.95} * SE$

substituting values

$K = [0.08 - 0.07 ] \pm 1.96 *0.0186$

$K = - 0.0265 \ or \ K = 0.0465$

The interval of the difference between proportions of improperly broken microchips for the two breaking methods is

$- 0.0265\le K \le 0.0465$

3 0

2 years ago

Suppose a lawn and garden company wants to determine the current percentage of customers who use fertilizer on their lawns. How

marishachu [46]

Answer:

n=601

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".

The population proportion have the following distribution

$p \sim N(p,\sqrt{\frac{\hat p(1-\hat p)}{n}})$

In order to find the critical value we need to take in count that we are finding the interval for a proportion, so on this case we need to use the z distribution. Since our interval is at 95% of confidence, our significance level would be given by $\alpha=1-0.95=0.05$ and $\alpha/2 =0.025$ . And the critical value would be given by:

$z_{\alpha/2}=-1.96, z_{1-\alpha/2}=1.96$

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

$\hat p \pm z_{\alpha/2}\sqrt{\frac{\hat p (1-\hat p)}{n}}$

The margin of error for the proportion interval is given by this formula:

$ME=z_{\alpha/2}\sqrt{\frac{\hat p (1-\hat p)}{n}}$ (a)

And on this case we have that $ME =\pm 0.04$ and we are interested in order to find the value of n, if we solve n from equation (a) we got:

$n=\frac{\hat p (1-\hat p)}{(\frac{ME}{z})^2}$ (b)

Since we don't have a prior estimation for the proportion we can use 0.5 as estimation. And replacing into equation (b) the values from part a we got:

$n=\frac{0.5(1-0.5)}{(\frac{0.04}{1.96})^2}=600.25$

And rounded up we have that n=601

3 0

2 years ago

Nina saved money in her piggy bank to buy a music player she started by saving 30$ that she received for her birthday and then s

Sedbober [7]

Answer:

No, it does not represent a proportional relationship.

Step-by-step explanation:

The ratios do not reduce to the same value.

40/1 = 40

50/2 = 25

60/3 = 20

We can also tell straight away that this is not a proportional relationship because Nina starts with $30. If the data were graphed, this would mean that the line would not go through the origin. It would start at 30 on the y axis.

6 0

3 years ago

Read 2 more answers

How do you simplify the expression 6(3-y)

Crank

Subtract 3 from y you get 6(-y)
6*y=6y

5 0

3 years ago

Read 2 more answers

Given p(x)=−4(x−15)2+2 , what us the value of p(7)?

zvonat [6]

P(x)=-4(x-15)2+2
P(x)=7
P(7)=-4(7-15)2+2
-4*7-4*-15
P(7)=-28+60+2+2
P(7)=92

5 0

2 years ago