Simplify the expression.<br><br> (–2

A random sample of 20 students yielded a mean of ¯x = 72 and a variance of s2 = 16 for scores on a college placement test in mat

Helen [10]

Answer:

The 98% confidence interval for the variance in the pounds of impurities would be $8.400 \leq \sigma^2 \leq 39.827$ .

Step-by-step explanation:

1) Data given and notation

$s^2 =16$ represent the sample variance

s=4 represent the sample standard deviation

$\bar x$ represent the sample mean

n=20 the sample size

Confidence=98% or 0.98

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 mean or variance 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.

The Chi square distribution is the distribution of the sum of squared standard normal deviates .

2) Calculating the confidence interval

The confidence interval for the population variance is given by the following formula:

$\frac{(n-1)s^2}{\chi^2_{\alpha/2}} \leq \sigma^2 \leq \frac{(n-1)s^2}{\chi^2_{1-\alpha/2}}$

On this case the sample variance is given and for the sample deviation is just the square root of the sample variance.

The next step would be calculate the critical values. First we need to calculate the degrees of freedom given by:

$df=n-1=20-1=19$

Since the Confidence is 0.98 or 98%, the value of $\alpha=0.02$ and $\alpha/2 =0.01$ , and we can use excel, a calculator or a table to find the critical values.

The excel commands would be: "=CHISQ.INV(0.01,19)" "=CHISQ.INV(0.99,19)". so for this case the critical values are:

$\chi^2_{\alpha/2}=36.191$

$\chi^2_{1- \alpha/2}=7.633$

And replacing into the formula for the interval we got:

$\frac{(19)(16)}{36.191} \leq \sigma^2 \leq \frac{(19)(16)}{7.633}$

$8.400 \leq \sigma^2 \leq 39.827$

So the 98% confidence interval for the variance in the pounds of impurities would be $8.400 \leq \sigma^2 \leq 39.827$ .

7 0

4 years ago

GEOMETRY HELP! <br><br> This is my last question and I don’t know what the answer is! Please help!

Angelina_Jolie [31]

Temporarily subdivide the given area into two parts: a large rectangle and a parallelogram. Find the areas of these two shapes separately and then combine them for the total area of the figure.

By counting squares on the graph, we see that the longest side of the rectangle is the hypotenuse of a triangle whose legs are 8 and 2. Applying the Pyth. Thm., we find that this length is √(8^2+2^2), or √68. Similarly, we find the the width of this rectangle is √(17). Thus, the area of the rectangle is √(17*68), or 34 square units.

This leaves the area of the parallelogram to be found. The length of one of the longer sides of the parallelogram is 6 and the width of the parallelogram is 1. Thus, the area of the parallelogram is A = 6(1) = 6 square units.

The total area of the given figure is then 34+6, or 40, square units.

7 0

4 years ago

At a zoo, the lion pen has a ring-shaped sidewalk around it. The outer edge of the sidewalk is a circle (blue) with a radius of

soldier1979 [14.2K]

Answer:

380

Step-by-step explanation:

11^2 x 3.14 = 380

5 0

4 years ago

Suppose the solution x=6 increases to x=9 and the left side of the equation stays the same. How would the right side need to cha

hoa [83]

Given that solution for some equation is x=6

Now they want to change x=6 into x=9.

Notice that all equations contans equal sign (=) because both side values are always same.

So if by any chance you want to change value of one side then you must change value on other side too

like we see that 6 changed to 9 by adding 3 on right side then we must add 3 on the left side too

so we get:

x=6

x+3=6+3

x+3=9

Now question says that the left side of the equation stays the same. That is possible only if we move +3 to the right side from the left side so we can write;

x=9-3

8 0

3 years ago

Mandy and Pete have a biased spinner numbered 1, 2, 3, 4, 5. They each want to find an estimate for the probability that the spi

kotykmax [81]

Answer:

Pete

Step-by-step explanation:

Given that:

Mandy's Estimate :

Number of spins , n = 20

Pete's Estimate:

Number of spins, n = 200

A good probability estimate is one which has narrow margin of error with a high degree of confidence. These two variables are affected by sample size.

A high sample size give a narrower margin of error and increases the confidence level probability

Based on the sample size used by each of Pete and Mandy, we can conclude that, Pete's probability estimate would be better due to its significantly higher sample size.

5 0

3 years ago

Simplify the expression. (–2 – c)(–1)