Ifx=−8, evaluate the following expression:(x−2)(x+4)x(x+9)

An analyst from an energy research institute in California wishes to precisely estimate a 99% confidence interval of the average

Lena [83]

Answer:

190

Step-by-step explanation:

Data provided in the question:

Confidence level = 99%

Therefore,

α = 1% = 0.01

[ from standard normal table ]

z-value for $z_{\frac{\alpha}{2}}= z_{\frac{0.01}{2}}=$ = 2.58

Margin of error, E = $0.06

Standard deviation, σ = $0.32

Now,

n = $(\frac{z_{0.005}\sigma}{E})^2$

Here,

n is the sample size (or the minimum number of gas stations )

on substituting the respective values, we get

= $(\frac{z_{0.005}\sigma}{E})^2$

= $(\frac{2.58\times0.32}{0.06})^2$

= 13.76²

= 189.3376 ≈ 190

Hence,

minimum number of gas stations that she should include in her sample is 190

5 0

2 years ago

A photoconductor film is manufactured at a nominal thickness of 25 mils. The product engineer wishes to increase the mean speed

Natali [406]

Answer:

$t=\frac{1.17-1.04}{\sqrt{\frac{0.11^2}{8}+\frac{0.09^2}{8}}}}=2.587$

$df=n_{1}+n_{2}-2=8+8-2=14$

Since is a one sided test the p value would be:

$p_v =P(t_{(14)}>2.587)=0.0108$

If we compare the p value and the significance level given $\alpha=0.05$ we see that $p_v$ so we can conclude that we have enough evidence to reject the null hypothesis, we have enough evidence to reject the null hypothesis on this case and the 25 mil film have a mean greater than the 20 mil film so then the claim is not appropiate

Step-by-step explanation:

Data given and notation

$\bar X_{1}=1.17$ represent the mean for the sample 1 (25 mil film)

$\bar X_{2}=1.04$ represent the mean for the sample 2 (20 mil film)

$s_{1}=0.11$ represent the sample standard deviation for the sample 1

$s_{2}=0.09$ represent the sample standard deviation for the sample 2

$n_{1}=8$ sample size selected for 1

$n_{2}=8$ sample size selected for 2

$\alpha=0.05$ represent the significance level for the hypothesis test.

t would represent the statistic (variable of interest)

$p_v$ represent the p value for the test (variable of interest)

State the null and alternative hypotheses.

We need to conduct a hypothesis in order to check if reducing the film thickness increases the mean speed of the film, the system of hypothesis would be:

Null hypothesis: $\mu_{1} \leq \mu_{2}$

Alternative hypothesis: $\mu_{1} > \mu_{2}$

If we analyze the size for the samples both are less than 30 so for this case is better apply a t test to compare means, and the statistic is given by:

$t=\frac{\bar X_{1}-\bar X_{2}}{\sqrt{\frac{s^2_{1}}{n_{1}}+\frac{s^2_{2}}{n_{2}}}}$ (1)

t-test: "Is used to compare group means. Is one of the most common tests and is used to determine whether the means of two groups are equal to each other".

Calculate the statistic

We can replace in formula (1) the info given like this:

$t=\frac{1.17-1.04}{\sqrt{\frac{0.11^2}{8}+\frac{0.09^2}{8}}}}=2.587$

P-value

The first step is calculate the degrees of freedom, on this case:

$df=n_{1}+n_{2}-2=8+8-2=14$

Since is a one sided test the p value would be:

$p_v =P(t_{(14)}>2.587)=0.0108$

If we compare the p value and the significance level given $\alpha=0.05$ we see that $p_v$ so we can conclude that we have enough evidence to reject the null hypothesis, we have enough evidence to reject the null hypothesis on this case and the 25 mil film have a mean greater than the 20 mil film so then the claim is not appropiate

4 0

2 years ago

What is a cube root? A fourth root? A fifth root? Explain.

Gre4nikov [31]

A cube root is the factor that we multiply by itself 3 times to get that number . fourth root is a number that has to be multiplied 4 times by itself same with a fifth root but multiplied 5 times. most numbers have a cube root , 4th root and a fifth root .

8 0

2 years ago

Read 2 more answers

You plan to take $450 u.s. on a trip to south africa. how many rands is this if one u.s. dollar equals 3.70 rands?

Inga [223]

$1 = 3.70 rands

$450 is simply 450 times $1, so multiply the conversion equation above by 450 on both sides.

450 * $1 = 450 * 3.70 rands

$450 = 1665 rands

8 0

2 years ago

Which line is perpendicular to 5x + 4y = 8?

bixtya [17]

It would be C) 5y = -4x -15

3 0

3 years ago