Mathematics : asked on ayrias
 13.10.2020

Find the standard deviation of the following set of data

. 4

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Mathematics
Step-by-step answer
P Answered by PhD

Explained below.

Step-by-step explanation:

The question is:

Compare the distributions using either the means and standard deviations or the five-number summaries. Justify your choice.

Set A: {36, 51, 37, 42, 54, 39, 53, 42, 46, 38, 50, 47}

Set B: {22, 57, 46, 24, 31, 41, 64, 50, 28, 59, 65, 38}

The five-number summary is:

MinimumFirst Quartile Median Third Quartile Maximum

The five-number summary for set A is:

Variable   Minimum       Q₁         Median        Q₃         Maximum

  Set A       36.00       38.25        44.00       50.75        54.00

The five-number summary for set B is:

Variable   Minimum       Q₁         Median        Q₃         Maximum

 Set B         22.00      28.75        48.00       58.50         65.00

Compute the mean for both the data as follows:

Mean_{A}=\frac{1}{12}\times [36+51+37+...+47]=44.58\approx 44.6\\\\Mean_{B}=\frac{1}{12}\times [22+57+46+...+38]=44.58\approx 44.6

Both the distribution has the same mean.

Compare mean and median for the two data:

Mean_{A}Median_{A}\\\\Mean_{B}Median_{B}

This implies that set A is positively skewed whereas set B is negatively skewed.

Compute the standard deviation for both the set as follows:

SD_{A}=\sqrt{\frac{1}{12-1}\times [(36-44.6)^{2}+...+(47-44.6)^{2}]}=6.44\approx 6.4\\\\SD_{B}=\sqrt{\frac{1}{12-1}\times [(22-44.6)^{2}+...+(38-44.6)^{2}]}=15.56\approx 15.6

The set B has a greater standard deviation that set A. Implying set B has a greater variability that set B.
Mathematics
Step-by-step answer
P Answered by PhD

Explained below.

Step-by-step explanation:

The question is:

Compare the distributions using either the means and standard deviations or the five-number summaries. Justify your choice.

Set A: {36, 51, 37, 42, 54, 39, 53, 42, 46, 38, 50, 47}

Set B: {22, 57, 46, 24, 31, 41, 64, 50, 28, 59, 65, 38}

The five-number summary is:

MinimumFirst Quartile Median Third Quartile Maximum

The five-number summary for set A is:

Variable   Minimum       Q₁         Median        Q₃         Maximum

  Set A       36.00       38.25        44.00       50.75        54.00

The five-number summary for set B is:

Variable   Minimum       Q₁         Median        Q₃         Maximum

 Set B         22.00      28.75        48.00       58.50         65.00

Compute the mean for both the data as follows:

Mean_{A}=\frac{1}{12}\times [36+51+37+...+47]=44.58\approx 44.6\\\\Mean_{B}=\frac{1}{12}\times [22+57+46+...+38]=44.58\approx 44.6

Both the distribution has the same mean.

Compare mean and median for the two data:

Mean_{A}Median_{A}\\\\Mean_{B}Median_{B}

This implies that set A is positively skewed whereas set B is negatively skewed.

Compute the standard deviation for both the set as follows:

SD_{A}=\sqrt{\frac{1}{12-1}\times [(36-44.6)^{2}+...+(47-44.6)^{2}]}=6.44\approx 6.4\\\\SD_{B}=\sqrt{\frac{1}{12-1}\times [(22-44.6)^{2}+...+(38-44.6)^{2}]}=15.56\approx 15.6

The set B has a greater standard deviation that set A. Implying set B has a greater variability that set B.
Mathematics
Step-by-step answer
P Answered by PhD

Explained below.

Step-by-step explanation:

(10)

The data set is:

S = {124, 94, 129, 109, 114}

The mean and standard deviation are:

\bar x=\frac{1}{n}\sum x=\frac{1}{5}\times [124+94+...+114]=114\\\\s=\sqrt{\frac{1}{n-1}\sum ( x-\bar x)^{2}}

  =\sqrt{\frac{1}{5-1}\times [(124-114)^{2}+(94-114)^{2}+...+(114-114)^{2}]}\\=\sqrt{\frac{750}{4}}\\=13.6931\\\approx 13.69

The correct option is B.

(11)

According to the Empirical 95% of the data for a Normal distribution are within 2 standard deviations of the mean.

So, the adult male's height is in the same range as about 95% of the other adult males whose heights were measured.

The correct option is B.

(12)

Let the score be X.

Given:

μ = 100

σ = 26

X=\mu-2\sigma

    =100-(2\times 26)\\=100-52\\=48

The correct option is B.

(13)

Let X be the prices of a certain model of new homes.

Given: X\sim  N(150000, 2300^{2})

Compute the percentage of buyers who paid between $147,700 and $152,300 as follows:

P(147700

                                         =P(-1                                        

According to the 68-95-99.7, 68% of the data for a Normal distribution are within 1 standard deviations of the mean.

The correct option is D.

(14)

Compute the percentage of buyers who paid more than $154,800 as follows:

P(X154800)=P(\frac{X-\mu}{\sigma}\frac{154800-150000}{2400})

                                         =P(Z2)\\=0.975\\

According to the 68-95-99.7, 95% of the data for a Normal distribution are within 2 standard deviations of the mean. Then the percentage of data above 2 standard deviations of the mean will be 97.5% and below 2 standard deviations of the mean will be 2.5%.

The correct option is D.

(15)

The z-score is given as follows:

z=\frac{x-\mu}{\sigma}

Mathematics
Step-by-step answer
P Answered by PhD

Explained below.

Step-by-step explanation:

(10)

The data set is:

S = {124, 94, 129, 109, 114}

The mean and standard deviation are:

\bar x=\frac{1}{n}\sum x=\frac{1}{5}\times [124+94+...+114]=114\\\\s=\sqrt{\frac{1}{n-1}\sum ( x-\bar x)^{2}}

  =\sqrt{\frac{1}{5-1}\times [(124-114)^{2}+(94-114)^{2}+...+(114-114)^{2}]}\\=\sqrt{\frac{750}{4}}\\=13.6931\\\approx 13.69

The correct option is B.

(11)

According to the Empirical 95% of the data for a Normal distribution are within 2 standard deviations of the mean.

So, the adult male's height is in the same range as about 95% of the other adult males whose heights were measured.

The correct option is B.

(12)

Let the score be X.

Given:

μ = 100

σ = 26

X=\mu-2\sigma

    =100-(2\times 26)\\=100-52\\=48

The correct option is B.

(13)

Let X be the prices of a certain model of new homes.

Given: X\sim  N(150000, 2300^{2})

Compute the percentage of buyers who paid between $147,700 and $152,300 as follows:

P(147700

                                         =P(-1                                        

According to the 68-95-99.7, 68% of the data for a Normal distribution are within 1 standard deviations of the mean.

The correct option is D.

(14)

Compute the percentage of buyers who paid more than $154,800 as follows:

P(X154800)=P(\frac{X-\mu}{\sigma}\frac{154800-150000}{2400})

                                         =P(Z2)\\=0.975\\

According to the 68-95-99.7, 95% of the data for a Normal distribution are within 2 standard deviations of the mean. Then the percentage of data above 2 standard deviations of the mean will be 97.5% and below 2 standard deviations of the mean will be 2.5%.

The correct option is D.

(15)

The z-score is given as follows:

z=\frac{x-\mu}{\sigma}

Mathematics
Step-by-step answer
P Answered by PhD
Given:

The data shows the number of grams of fat found in 9 different health bars.

12, 14, 16, 17.5, 10, 18, 15, 15.5, 19

The IQR of the data is determined by first arranging the data according to their values, from lowest to highest:

10, 12, 14, 15, 15.5, 16, 17.5, 18, 19
 
IQR = 4.75 = Q3 - Q1

What is the range of the data set?

32, 21, 88, 64, 88, 107, 101

Again, rearrange the data according to value (lowest to highest), then find the minimum and maximum values:

Range = 21 to 107
Mathematics
Step-by-step answer
P Answered by Master

Considering the first statement

Standard deviation is resistive to unusual values    

 This statement is false because standard deviation is the numeric measure of deviation of the each observation from the mean

Considering the second  statement    

The standard deviation of a set of values is equal to 0 if and only if all of the values are the same.

This statement is true because standard deviation is the numeric measure of deviation of the each observation from the mean.

Considering the third  statement

Standard deviation is never negative.

This statement is true because standard deviation is the numeric measure of deviation of the each observation from the mean.

Considering the fourth statement

Changing the units of a set of values (e.g., converting from inches to feet) does not affect its standard deviation

 This statement is false because standard deviation is the numeric measure of deviation of the each observation from the mean

Considering the fifth  statement

If a set of values has a mean of 0 and a standard deviation that is not 0, then adding a new data point with a value of 0 will have no effect on the standard deviation.

This statement is false because , let take an example

    x     -4 - 3 0 3 4

Generally the mean is mathematically evaluated as

    \= x =  \frac{\sum x_i }{n}

=>   \= x =  \frac{-4+ (- 3)+ 0 + 3 + 4 }{5}

=>   \= x =  0

Generally the standard deviation is mathematically evaluated as      

     \sigma  =  \sqrt{\frac{\sum (x_ i - \= x )^2}{y} }

      \sigma  =  \sqrt{\frac{ (-4  - 0 )^2 + (- 3 - 0 )^2 + (0 - 0 )^2 + (3 - 0)^2 + (4 - 0 )^2}{5} }

=>        \sigma  = 3.16

Now when zero is removed the standard deviation is  

\sigma_1  =  \sqrt{\frac{ (-4  - 0 )^2 + (- 3 - 0 )^2 + (3 - 0)^2 + (4 - 0 )^2}{4} }

=>   \sigma_1  =  3.54

Since  \sigma  \ne  \sigma _1 the above statement is  false

Considering the sixth  statement

Standard deviation represents how far a group of values are from the mean of those values, on average.

This statement is true because standard deviation is the numeric measure of deviation of the each observation from the mean.

Step-by-step explanation:

Mathematics
Step-by-step answer
P Answered by PhD
Given:

The data shows the number of grams of fat found in 9 different health bars.

12, 14, 16, 17.5, 10, 18, 15, 15.5, 19

The IQR of the data is determined by first arranging the data according to their values, from lowest to highest:

10, 12, 14, 15, 15.5, 16, 17.5, 18, 19
 
IQR = 4.75 = Q3 - Q1

What is the range of the data set?

32, 21, 88, 64, 88, 107, 101

Again, rearrange the data according to value (lowest to highest), then find the minimum and maximum values:

Range = 21 to 107

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