Answer:
(a) The sample variance is 16.51
(a) The sample standard deviation is 4.06
Step-by-step explanation:
Given
![\begin{array}{cc}{Class} & {Frequency} & 8.26 - 10.00 & 20 &10.01-11.75 & 38 &11.76 - 13.50& 36 & 13.51-15.25 &25&15.26-17.00 &27 &\ \end{array}](https://tex.z-dn.net/?f=%5Cbegin%7Barray%7D%7Bcc%7D%7BClass%7D%20%26%20%7BFrequency%7D%20%26%208.26%20-%2010.00%20%26%2020%20%2610.01-11.75%20%26%2038%20%2611.76%20-%2013.50%26%2036%20%26%2013.51-15.25%20%2625%2615.26-17.00%20%2627%20%26%5C%20%5Cend%7Barray%7D)
Solving (a); The sample variance.
First, calculate the class midpoints.
This is the mean of the intervals.
i.e.
![x_1 = \frac{8.26+10.00}{2} = \frac{18.26}{2} = 9.13](https://tex.z-dn.net/?f=x_1%20%3D%20%5Cfrac%7B8.26%2B10.00%7D%7B2%7D%20%3D%20%5Cfrac%7B18.26%7D%7B2%7D%20%3D%209.13)
![x_2 = \frac{10.01+11.75}{2} = \frac{21.76}{2} = 10.88](https://tex.z-dn.net/?f=x_2%20%3D%20%5Cfrac%7B10.01%2B11.75%7D%7B2%7D%20%3D%20%5Cfrac%7B21.76%7D%7B2%7D%20%3D%2010.88)
![x_3 = \frac{11.76+13.50}{2} = \frac{25.26}{2} = 12.63](https://tex.z-dn.net/?f=x_3%20%3D%20%5Cfrac%7B11.76%2B13.50%7D%7B2%7D%20%3D%20%5Cfrac%7B25.26%7D%7B2%7D%20%3D%2012.63)
![x_4 = \frac{13.51+15.25}{2} = \frac{28.76}{2} = 14.38](https://tex.z-dn.net/?f=x_4%20%3D%20%5Cfrac%7B13.51%2B15.25%7D%7B2%7D%20%3D%20%5Cfrac%7B28.76%7D%7B2%7D%20%3D%2014.38)
![x_5 = \frac{15.26+17.00}{2} = \frac{32.26}{2} = 16.13](https://tex.z-dn.net/?f=x_5%20%3D%20%5Cfrac%7B15.26%2B17.00%7D%7B2%7D%20%3D%20%5Cfrac%7B32.26%7D%7B2%7D%20%3D%2016.13)
So, the table becomes:
![\begin{array}{ccc}{Class} & {Frequency} & {x} & 8.26 - 10.00 & 20&9.13 &10.01-11.75 & 38 &10.88&11.76 - 13.50& 36 &12.63& 13.51-15.25 &25&14.38&15.26-17.00 &27 &16.13\ \end{array}](https://tex.z-dn.net/?f=%5Cbegin%7Barray%7D%7Bccc%7D%7BClass%7D%20%26%20%7BFrequency%7D%20%26%20%7Bx%7D%20%26%208.26%20-%2010.00%20%26%2020%269.13%20%2610.01-11.75%20%26%2038%20%2610.88%2611.76%20-%2013.50%26%2036%20%2612.63%26%2013.51-15.25%20%2625%2614.38%2615.26-17.00%20%2627%20%2616.13%5C%20%5Cend%7Barray%7D)
Next, calculate the mean
![\bar x = \frac{\sum fx}{\sum f}](https://tex.z-dn.net/?f=%5Cbar%20x%20%3D%20%5Cfrac%7B%5Csum%20fx%7D%7B%5Csum%20f%7D)
![\bar x = \frac{20*9.13 + 38 * 10.88+36*12.63+25*14.38+27*16.13}{20+38+36+25+27}](https://tex.z-dn.net/?f=%5Cbar%20x%20%3D%20%5Cfrac%7B20%2A9.13%20%2B%2038%20%2A%2010.88%2B36%2A12.63%2B25%2A14.38%2B27%2A16.13%7D%7B20%2B38%2B36%2B25%2B27%7D)
![\bar x = \frac{1845.73}{146}](https://tex.z-dn.net/?f=%5Cbar%20x%20%3D%20%5Cfrac%7B1845.73%7D%7B146%7D)
![\bar x = 12.64](https://tex.z-dn.net/?f=%5Cbar%20x%20%3D%2012.64)
Next, the sample variance is:
![\sigma^2 = \frac{\sum f(x - \bar x)^2}{\sum f - 1}](https://tex.z-dn.net/?f=%5Csigma%5E2%20%3D%20%5Cfrac%7B%5Csum%20f%28x%20-%20%5Cbar%20x%29%5E2%7D%7B%5Csum%20f%20-%201%7D)
So, we have:
![\sigma^2 = \frac{20*(9.13-12.63)^2 + 38 * (10.88-12.63)^2 +...........+27 * (16.13 -12.63)^2}{20+38+36+25+27-1}](https://tex.z-dn.net/?f=%5Csigma%5E2%20%3D%20%5Cfrac%7B20%2A%289.13-12.63%29%5E2%20%2B%2038%20%2A%20%2810.88-12.63%29%5E2%20%2B...........%2B27%20%2A%20%2816.13%20-12.63%29%5E2%7D%7B20%2B38%2B36%2B25%2B27-1%7D)
![\sigma^2 = \frac{2393.6875}{145}](https://tex.z-dn.net/?f=%5Csigma%5E2%20%3D%20%5Cfrac%7B2393.6875%7D%7B145%7D)
![\sigma^2 = 16.51](https://tex.z-dn.net/?f=%5Csigma%5E2%20%3D%2016.51)
The sample standard deviation is:
![\sigma = \sqrt{\sigma^2}](https://tex.z-dn.net/?f=%5Csigma%20%3D%20%5Csqrt%7B%5Csigma%5E2%7D)
![\sigma = \sqrt{16.51}](https://tex.z-dn.net/?f=%5Csigma%20%3D%20%5Csqrt%7B16.51%7D)
![\sigma = 4.06](https://tex.z-dn.net/?f=%5Csigma%20%3D%204.06)
B. It would be 5/2 and -3/4.
<span>The answer is 7. Seven is a prime number, which means that its multiples are 1 and itself (7): 7 = 1 * 7. To find out which one is a factor of 7, we should divide each of them by 7. 1/7 will be a decimal number and 7/7 = 1, which is a whole number. Thus, 7 will be a multiple of 7 and also a factor of 7.Hope this helps. Let me know if you need additional help!</span>