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3 years ago

I need to know the answer

Mathematics

1 answer:

sergiy2304 [10]3 years ago

8 0

14.1 is the correct answer i just calculated it and then subtracted

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Various problems with data collection can cause some observations to be missing. Suppose a data set has 20 cases. Here are the v

mr Goodwill [35]

Answer:

a) Mean= 15, standard deviation= 5.1575

b) Mean= 15, standard deviation= 3.6469

c) See below

Step-by-step explanation:

(a) Compute the mean and standard deviation for the 10 cases for which x is not missing.

The mean using the ten known values is

$\bar x=\frac{17+6+12+14+20+23+9+12+16+21}{10}=15$

The standard deviation is

$\small s=\sqrt{\frac{(17-15)^2+(6-15)^2+(12-15)^2+(14-15)^2+(20-15)^2+(23-15)^2+(9-15)^2+(12-15)^2+(16-15)^2+(21-15)^2}{10}}=5.1575$

(b) Create a new data set with 20 cases by using imputation where you set the values for the 10 missing cases equal to the mean that you computed in the previous part. Compute the mean and standard deviation for this new data set with 20 cases.

The new data set would be

17, 6, 12, 14, 20, 23, 9, 12, 16, 21, 15, 15, 15, 15, 15, 15, 15, 15, 15, 15

The new mean for this set of values would be then

$\bar x=\frac{\displaystyle\sum_{i=1}^{20}x_i}{20}=15$

The new standard deviation is now

$s=\sqrt{\frac{\displaystyle\sum_{i=1}^{20}(x_i-\bar x)^2}{20}}=3.6469$

(c) Summarize what you have learned about the possible effects of this type of imputation on the mean and the standard deviation.

Obviously, this way of imputation is somewhat arbitrary and will produce a set of data undoubtedly skewed.

It could possibly be a sensible way of imputing data if the amount of missing data is very little compared to the whole set, for example one or two data in a set of 100, but in this case we have 50% of missing data and it makes no sense this procedure.

4 0

3 years ago

Let A = −2 2 1 −3 1 1 2 0 −1 and B = 2 −1 0 1 2 1 −1 −2 4 . Use the matrix-column representation of the product to write each co

BigorU [14]

Answer:

AB = $\left[\begin{array}{ccc}-3&4&6\\-6&3&5\\5&0&-4\end{array}\right]$

Each column of AB is written as a linear combination of columns of Matrix A in the explanation below.

Step-by-step explanation:

A = $\left[\begin{array}{ccc}-2&2&1\\-3&1&1\\2&0&-1\end{array}\right]$

B= $\left[\begin{array}{ccc}2&-1&0\\1&2&1\\-1&-2&4\end{array}\right]$

We need to write each column of AB as a linear combination of the columns of A so we will multiply each column of A with each column element of B to get the column of AB. So,

AB Column 1 = 2 * $\left[\begin{array}{ccc}-2\\-3\\2\end{array}\right]$ + 1 $\left[\begin{array}{ccc}2\\1\\0\end{array}\right]$ + (-1) $\left[\begin{array}{ccc}1\\1\\-1\end{array}\right]$ = $\left[\begin{array}{ccc}-3\\-6\\5\end{array}\right]$

AB Column 2 = (-1) $\left[\begin{array}{ccc}-2\\-3\\2\end{array}\right]$ + 2 $\left[\begin{array}{ccc}2\\1\\0\end{array}\right]$ + (-2) $\left[\begin{array}{ccc}1\\1\\-1\end{array}\right]$ = $\left[\begin{array}{ccc}4\\3\\0\end{array}\right]$

AB Column 3 = (0) $\left[\begin{array}{ccc}-2\\-3\\2\end{array}\right]$ + (1) $\left[\begin{array}{ccc}2\\1\\0\end{array}\right]$ + 4 $\left[\begin{array}{ccc}1\\1\\-1\end{array}\right]$ = $\left[\begin{array}{ccc}6\\5\\-4\end{array}\right]$

Finally, we can combine all three columns of AB to form the 3x3 matrix AB.

AB = $\left[\begin{array}{ccc}-3&4&6\\-6&3&5\\5&0&-4\end{array}\right]$

4 0

4 years ago

What expression is equivalent to (2/x-4/y)/(-5/y+3/x)

kirill115 [55]

-2 * (2x - y) / 3y - 5x

I don't really know how to explain it but this is the answer to wh<span>at expression is equivalent to (2/x-4/y)/(-5/y+3/x)</span>

8 0

3 years ago

Del ray can run 20 1/2 miles in 2 1/4 hours. How many miles per hour can he run?

emmasim [6.3K]

$20 \frac{1}{2} :2 \frac{1}{4} = \frac{41}{2}: \frac{9}{4}= \frac{41}{2}* \frac{4}{9} =\frac{82}{9} = 9 \frac{1}{9} \ \ \text{miles per hour}$

5 0

3 years ago

Is this the correct answer, yall?

ehidna [41]

Yes, yes it is; well done.

4 0

3 years ago