The table below shows the frequency distribution for 12 stud

The table below shows the frequency distribution for 12 students on a test with a maximum score of 20. Use this sample data to answer questions 6 through 8: What is the mean score, X, of the data in the frequency distribution above The standard deviation of the scores of the frequency distribution above The median score lies in which score intervel? 1-5 6-10 11-15 16-20 Nine horses are in a race and the top three winners, in order, are announced: Blizer (1); Southerm Cross (2); Smoke House (3). My Uncle Roger knows nothing about horses: What is the probability of him randomly picking three horses and winning the Trifecta? (i.e. the probability of picking those exact three horses in that exact order?) qC3 / qP3 1/qP3 qP3/qC3 answer not listed

Solution

Consider:

6.

Thus,  
  
Mean = Sum(xf) / Sum(f) =    13.41666667 [ANSWER]

7.

Variance = [Sum(x^2f) - Sum(xf)^2/Sum(f)]/[Sum(f)-1] =    24.81060606

Thus,

Standard deviation = sqrt(Variance) =    4.981024599 [ANSWER]

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8.

There are 12 observations, so the median is the average of the 6th and 7th lowest observations. So, it has to be in

OPTION C: 11-15 [ANSWER]

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9.

Order matters, so there are 9P3 ways to guess. Hence,

P = 1/(9P3) [ANSWER, B]

Consider the table:
x (midpoint)	f	x f	x^2 f
3	1	3	9
8	2	16	128
13	4	52	676
18	5	90	1620