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Deffense [45]
3 years ago
13

A college administrator would like to estimate the average grade point average (average of GPA) of all the current registered st

udents based on a random sample. He plans to estimate the average GPA to within 0.05 with 90% confidence interval. At least how many students does he need to include in the sample in order to accomplish that? Assume the standard deviation of all GPA's in the student population is \sigma σ = 0.4.
Mathematics
1 answer:
bonufazy [111]3 years ago
8 0

Answer: 346

Step-by-step explanation:

Given :  Margin of error : E= 0.05

Standard deviation : \sigma=0.4

Significance level :\alpha=1-0.9=0.1

Critical value : z_{\alpha/2}=1.645

The formula to calculate sample size ( if proportion is known) :-

n=(\dfrac{z_{\alpha/2}\sigma}{E})^2\\\\\Rightarrow\ n=(\dfrac{(2.326\times0.4)}{0.05})^2\\\\\Rightarrow\ n=346.257664\approx346

Hence, the required minimum sample would be 346.

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What is the value of m in the figure below in this diagram abd bcd
oee [108]

\triangle BCA\ \text{and}\ \triangle DCB\ \text{are similar (AAA). Therefore the sides are in proportion:}\\\\\dfrac{BC}{CD}=\dfrac{AC}{BC}\\\\\text{We have}\\\\BC=m\\CD=7\\AC=7+11=18\\\\\text{Substitute:}\\\\\dfrac{m}{7}=\dfrac{18}{m}\qquad\text{cross multiply}\\\\m^2=(7)(18)\\\\m^2=126\to\boxed{m=\sqrt{126}}\to\boxed{A.}

6 0
4 years ago
The number of free song downloads is determined using a ratio when you purchase 40 songs you get 24 free song downloads how many
natka813 [3]
34 because 24 is 6x4 and 40 is 6.5 but you obviously round up so 7x6 so18 free songs is is 6x3 you just take away 6 to your number so 40-6+=34 so 34
3 0
3 years ago
A speedometer has a percent error of 10%. The actual speed of the car is 40 mph. Select from the drop-down menus to correctly co
rodikova [14]

Answer

Answer

The speedometer is likely to show the speed is either 36.0 mph or 44.0 mph.        

To prove

Formula

Percentage\ error = \frac{error\times 100}{Exact\ value}

Where error = |Approx value - Exact value |

First case

As given

A speedometer has a percent error of 10%. The actual speed of the car is 40 mph.    

Here

Percentage error = 10%

Exact value = 40 mph

error = - (Approx value - Exact value )

          = - (Approx value - 40 )

          = - Approx value + 40

Put in the formula

10 = \frac{(-Approx\ value + 40)\times 100}{40}

400 = {(-Approx\ value + 40)\times 100}

\frac{400}{100} =-Approx\ value + 40      

\4 =-Approx\ value + 40      

Thus

Approx value = 40 - 4

Approx value = 36 mph

Therefore Option (b) is correct .

Second Case

error =  (Approx value - Exact value )

          =  (Approx value - 40 )

          =  Approx value - 40

Put in the formula

10 = \frac{(Approx\ value - 40)\times 100}{40}

400 = {(Approx\ value - 40)\times 100}

\frac{400}{100} = Approx\ value - 40      

\4 = Approx\ value - 40      

Thus

Approx value = 40 + 4

Approx value = 44 mph

Therefore Option (c) is correct .

4 0
3 years ago
Sandra calculated her taxable income as $39,250. She paid $6,000 in federal withholding tax. And you are single Your tax is If l
True [87]

Answer: 56

Step-by-step explanation:

6,000-5,944=

because 6,000 is how much she paid, but she only owed 5,944 so the the difference is what her refund is.

4 0
3 years ago
When the population distribution is normal, the statistic median {|X1 − X tilde|, . . . , |Xn − X tilde|}/0.6745 can be used to
Andreyy89

Answer:

The corresponding point estimate is 0.882.

The sample standard deviation is 1.373.

Step-by-step explanation:

The data set is:

S = {25.01, 25.87, 26.34, 26.51, 26.75, 27.24, 27.40, 27.63, 27.83, 27.90, 28.08, 28.13, 28.37, 28.58, 28.59, 28.96, 29.20, 29.22, 29.38, 30.88}

Compute the mean as follows:

\bar X=\frac{1}{n}\sum X\\\\=\frac{1}{20}\times [25.01+25.87+...+30.88]\\\\=\frac{1}{20}\times 557.87\\\\=27.8935

Subtract the mean from each value and take the modulus of those values.

The new data set is:

S₁ = {2.8835, 2.0235, 1.5535, 1.3835, 1.1435, 0.6535, 0.4935, 0.2635, 0.0635, 0.0065, 0.1865, 0.2365, 0.4765, 0.6865, 0.6965, 1.0665, 1.3065, 1.3265, 1.4865, 2.9865}

Arrange these values in ascending order as follows:

S₂ = {0.0065 , 0.0635 , 0.1865 , 0.2365 , 0.2635 , 0.4765 , 0.4935 , 0.6535 , 0.6865 , 0.6965 , 1.0665 , 1.1435 , 1.3065 , 1.3265 , 1.3835 , 1.4865 , 1.5535 , 2.0235 , 2.8835 , 2.9865}

There are 20 observations in the data set.

The median value for an even set of values is the mean of the middle two values.

In this case the median will be the mean of the 10th and 11th observations.

\text{Median}=\frac{10^{th}obs.+11^{th}obs.}{2}=\frac{0.6965+1.0665}{2}=0.8815\approx 0.882

Thus, the corresponding point estimate is 0.882.

Compute the standard deviation as follows:

In set S₁ we computed the absolute mean deviations.

Now take the square of these values and divide by (n - 1) to compute the sample variance:

\sigma^{2}=\frac{1}{n-1}\sum (|X_{i}-\bar X|)^{2}

     =\frac{1}{20-1}\times [(2.8835)^{2}+(2.0235)^{2}+...+(2.9865)^{2}]\\\\=\frac{1}{19}\times 35.7953\\\\=1.88396

Compute the sample standard deviation as follows:

\sigma=\sqrt{\sigma^{2}}=\sqrt{1.88396}=1.373

Thus, the sample standard deviation is 1.373.

6 0
3 years ago
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