PLzzzzzzz helppppppppp!!!

A chemist examines 15 geological samples for potassium chloride concentration. The mean potassium chloride concentration for the

NikAS [45]

Answer:

$0.376-2.145\frac{0.0012}{\sqrt{15}}=0.375$

$0.376+2.145\frac{0.0012}{\sqrt{15}}=0.377$

And we are 95% confident that the true mean of chloride concentration is between 0.375 and 0.377 cc/ cubic meter

Step-by-step explanation:

Data provided

$\bar X=0.376$ represent the sample mean for the chloride concentration

$\mu$ population mean (variable of interest)

s=0.0012 represent the sample standard deviation

n=15 represent the sample size

Confidence interval

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

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

Since we need to find the critical value first we need to begin finding the degreed of freedom

$df=n-1=15-1=14$

The Confidence is 0.95 or 95%, the significance would be $\alpha=0.05$ and $\alpha/2 =0.025$ , and the critical value for this case with a t distribution with 14 degrees of freedom is $t_{\alpha/2}=2.145$

And the confidence interval is:

$0.376-2.145\frac{0.0012}{\sqrt{15}}=0.375$

$0.376+2.145\frac{0.0012}{\sqrt{15}}=0.377$

And we are 95% confident that the true mean of chloride concentration is between 0.375 and 0.377 cc/ cubic meter

7 0

4 years ago

PLEASE HELP..... I WILL GIVE BRAINLIEST!!

Yakvenalex [24]

For the first part:

Every shirt she grabs, will cost her dollars, so if she grabs 3 shirts, then the cost of the shirts is:

$12+12+12=3(12)$

With the same rationale, if she grabs 2 pairs of jeans, the cost of the jeans is:

$19+19=2(19)$

So, her total is:

$3(12)+2(19)$

If you subtract 3 from the total, then the expression is:

$3(12)+2(19)-3=36+38-3=71$

For the second part:

If she's paying 3 less for each shirt, then the cost of 3 shirts will become:

$(12-3)+(12-3)+(12-3)=3(12-3)$

In the same fashion, for the two jeans:

$(19-3)+(19-3)=2(19-3)$

So the expression for the total cost is:

$3(12-3)+2(19-3)=36-9+38-6=59$

For number three:

The amounts are different because the cost of the total purchase is different than the cost of each element that makes up the total purchase.

For number four:

If you're the owner, you want to give the smallest amount of discount (the one in part 1/a).

So you could clarify by saying there's 3 dollars of the TOTAL purchase's cost.

6 0

3 years ago

The shapes in this question are drawn on a centimetre grid.

xenn [34]

Answer:

A. 12 centimeters B. 4 centimeters C. 20 centimeters

Step-by-step explanation:

To find area you need to do the Height time the Length.

For A it is 3x4

For B it is 4x1

And for C it is 4x5

You get this equation by multiplying the amount of squares that the Height and Length measured!