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3 years ago

12 POINTS! HELP ASAP!!

Mathematics

1 answer:

Aleks [24]3 years ago

6 0

Answer:

(2,-4)

Step-by-step explanation:

When a point (x,y) is reflected across the y-axis, you need to change the sign of x. For example, if (-x,y) you need to take away the negative sign, which makes (x,y). Or, if the point is (x,y), you need to add a negative sign to the x, which makes (-x,y). So, if your point (-2, -4) is reflected across the y-axis, you need to take the negative sign off the -2, which makes (2,-4).

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12 is 30% of what?

alexgriva [62]

12 = 30% of what
12 = 0.30x
12 / 0.30 = x
40 = x.......so 12 is 30% of 40

5 0

4 years ago

A statistics professor plans classes so carefully that the lengths of her classes are uniformly distributed between 46.046.0 and

Gala2k [10]

Answer:

The probability of selecting a class that runs between 50.2550.25 and 51.2551.25 minutes is 0.10

Step-by-step explanation:

The Uniform Distribution, also known as Rectangular Distribution, is a type of Continuous Probability Distribution. It has a continuous random variable restricted to a finite interval and its probability function has a constant density during this interval.

The formula of probability if given by:

f(x)=

$\left \{ {{\frac{1}{b-a}; \ a \leq x \leq b } \atop {0}; \ x \ otherwise } \right.$

In this exercise a= 46.0 and b= 56.0

The probability of selecting a class that runs between 50.2550.25 and 51.2551.25 minutes is:

$\int\limits^{51.25}_{50.25} {\frac{1}{56-46} } \, dx = \int\limits^{51.25}_{50.25} {\frac{1}{10} } \, dx = \frac{1}{10} \times (51.25 - 50.25)=\frac{1}{10}=0.1$

7 0

3 years ago

In an examination of purchasing patterns of shoppers, a sample of 16 shoppers revealed that they spent, on average, $54 per hour

Lesechka [4]

Answer:

$54-1.64\frac{21}{\sqrt{16}}=45.39$

$54 +1.64\frac{21}{\sqrt{16}}=62.61$

So on this case the 90% confidence interval would be given by (45.39;62.61)

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".

$\bar X=54$ represent the sample mean

$\mu$ population mean (variable of interest)

$\sigma=21$ represent the sample standard deviation

n=16 represent the sample size

Solution to the problem

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

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

Since the Confidence is 0.90 or 90%, the value of $\alpha=1-0.9=0.1$ and $\alpha/2 =0.05$ , and we can use excel, a calculator or a table to find the critical value. The excel command would be: "=-NORM.INV(0.05,0,1)".And we see that $z_{\alpha/2}=1.64$