Random Variable and Standard Deviation

Topics: Random variable, Probability distribution, Probability theory Pages: 3 (560 words) Published: April 18, 2011
MATH 107NAME:_______________________
EXAM 2
Show all work for credit and keep answers exact when possible.

1. Classify the following statement as an example of classical, empirical, or subjective probability and explain your reasoning. According to your doctor he feels the chance of you surviving a surgery is 0.85.

Subjective; based upon his feelings.

2. Determine the two events described in the study. Do the results indicate that the events are independent or dependant? Researchers found that people with depression are five times more likely to have a breathing- related sleep disorder than people who are not depressed.

Depression and Breathing-related sleep disorders; Dependant

3. A horse race has 10 entries. Assuming that there are no ties, what is the probability that the three horses owned by one person finish first second, and third? The number of possible combinations of 3 horses winning, in any order, is

So the probability is

4. In how many distinguishable ways can the letters in the word statistics be written?

5. The table shows the results of a survey that asked 2850 people whether they are involved in any type of charity work. | Frequently| Occasionally| Not at all| Total|
Male| 221| 456| 795| 1472|
Female| 207| 430| 741| 1378|
Total| 428| 886| 1536| 2850|

A person is selected at random from the sample.

a) What is the probability the person is female or occasionally involved in charity work?

b) Are the events “being female and occasionally involved in charity work” and “being frequently involved in charity work” mutually exclusive? yes

6. A company gave psychological tests to perspective employees. The random variable x represents the possible test scores.

a) Use the histogram to find the probability that a person selected at random from the survey’s sample had a test score of more than two.

b) Find the probability that the person had a...

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