How to Find x value: 9-0.75(x+8)-5=-6.5

1 answer:

8 0

Here's how to find the value of x:

<span>9 - 0.75 ( x + 8 ) - 5 = -6.5 find the difference of 9 - 0.75

</span><span>8.25 ( x + 8 ) - 5 = -6.5 add 5 to both sides
</span>
8.25 ( x + 8 ) = -1.5 distribute 8.25 to x and 8

8.25x + 66 = -1.5 subtract 66 from both sides

8.25x = -67.5 divide both sides by 8.25

x = 18.18181818...... the value of x is 18 2/11

hope this helps

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Answer:

$652.6-2.01\frac{311.7}{\sqrt{50}}=563.997$

$652.6+2.01\frac{311.7}{\sqrt{50}}=741.203$

So on this case the 95% confidence interval would be given by (563.997;741.203)

Step-by-step explanation:

Previous concepts

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".

$\bar X=652.6$ represent the sample mean for the sample

$\mu$ population mean (variable of interest)

s=311.7 represent the sample standard deviation

n=50 represent the sample size

Soltuion to the problem

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:

$df=n-1=50-1=49$

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(0.025,49)".And we see that $t_{\alpha/2}=2.01$