SOLUTION: The following are the marks scored by 20 students in a test: 15 11 17 25 13 15 16 22 24 27 20 22 15 16 15 19 22 24 22 11 (a) Prepare a frequency table for th

Algebra.Com
Question 1210334: The following are the marks scored by 20 students in a test:
15 11 17 25 13 15 16 22 24 27
20 22 15 16 15 19 22 24 22 11
(a) Prepare a frequency table for the distribution using class intervals 10 - 12, 13 - 15, 16-18....
(b) Calculate the variance of the distribution.
(c) If the pass mark for the test was 16, find the probability that a student selected at random from the class failed.
Answer by mccravyedwin(406)   (Show Source): You can put this solution on YOUR website!
class
interval  freq  midpoint(xi)   
  10-12     2       11
  13-15     5       14
  16-18     3       17
  19-21     2       20
  22-24     6       23
  25-27     2       26

  

We calculate the variance:

xi       xi-mu     (xi-mu)^2                fi(xi-mu)^2
-----------------------------------------------------------
11       -7.65      58.5225           2(58.5225) = 117.045   
14       -4.65      21.6225           5(21.6225) = 108.1125  
17       -1.65       2.7225            3(2.7225) =   8.1675 
20        1.35       1.9225            2(1.8225) =   3.645  
23        4.35      18.9225           6(18.9225) = 113.535  
26        7.35      54.0225           2(54.0225) = 108.045  
-----------------------------------------------------------
                                                   458.65



(c) 
2 were in 10-12 and 5 were in 13-15, so 2+5=7 failed
P(failure) = 7/20 = 0.35

Edwin
RELATED QUESTIONS

There are 31 participants in a special high-adventure camp. Following is a list of the... (answered by solver91311)
What is the mean, mode, range,and standard deviation 11 26 11 12 27 20 29 7 26 18 22... (answered by Fombitz)
Here is another frequency question that I have been scratching my head over. Please... (answered by anantha)
what is the sum of all of these? 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20... (answered by Fombitz,Alan3354)
compute a one-sample t-test comparing the age of your sample to the age of the general... (answered by ikleyn)
The positive integers are arranged in the pattern illustrated below: 1 2 5 10 17 26 3 (answered by greenestamps)
Construct a frequency table with 5 classes. 16 , 15 , 16 , 14 , 16 , 1 , 16 ,... (answered by Fombitz)
In dyer need of assistance... PLEASE HELP A vendor is curious about the number of... (answered by jim_thompson5910)
Construct a frequency distribution of the ages that 25 randomly selected smokers started... (answered by Edwin McCravy)