Chapter 5 - Examples
1. A coin is tossed twice, with the sample space HH, HT, TH, and TT. Write the probability distribution for the number of tails (it's 0, 1, or 2).

2. In the experiment in number 1, find the probability that the number of tails is 1 or 2.

3. At Dalton State College, the number of students in the math lab at 12 noon is given a at right. So, the probability that there are 2 students in the math lab at 12 noon is 0.15 (in our notation, P(X= 2) = 0.15). Find the mean of students in the math lab at 12 noon.
(x) P(x)
00.50
10.25
20.15
30.07
40.03

4. For the given table, give the standard deviation for number of students in the math lab at 12 noon.
(x) P(X = x) x·P(X = x) x2 x2·P(X = x) Û x· [x·P(X = x)]
0 0.50 0.00 0 0.00
1 0.25 0.25 1 0.25
2 0.15 0.30 4 0.60
3 0.07 0.21 9 0.63
4 0.03 0.12 16 0.48
    0.88   1.96
 

 

 

 

 

 

5. Give the number .

6. The success of a student getting out of College Algebra is 50 %; this is nationally. What is the probability that in a class of 10 that you will get 3 who will pass the class?

7. You have taken a test on which the average was a 73; the distribution is normal. You made an 89; what is you z-score? (Your z-score is how many "standard deviations" you made from the average.)

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