Stats/Probability Theory REALLY

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In summary, the conversation discusses a joint probability mass function and finding the marginal distribution of X and E[XY]. There is some confusion about the notation and a suggestion to use the "Tex" program for future questions.
  • #1
playboy
Stats/Probability Theory REALLY need help :(

I really need some help.

I have a joint probability mass function...

P(X=x, Y=y) = (20Cx,y,20-x-y)(0.1)^x(0.3)^y(0.5)^(20-x-y)
where 0</= x + y </= 20

b) show that the margninal distribution of X is binomial
c) find E[XY]

Somebody please help me.

Thanks
 
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  • #2
I have no idea what "(20Cx,y,20-x-y)" means. I might guess that 20Cx is the binomial coefficient but since you haven't said that x and y must be integers it might not be.
 
  • #3
oh sorry that means choose

P(X=x, Y=y) = [(20)C(x,y,20-x-y)](0.1)^x(0.3)^y(0.5)^(20-x-y)
where 0</= x + y </= 20

and C means chosse...

Also, this question is about a DISCRETE random variable, so integrals won't work.

Over the holidays, i have to learn how to use that "Tex" programme or whatever its called... by the way, where could i actually get a tutorial on how to use that programme?
 
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FAQ: Stats/Probability Theory REALLY

What is the difference between statistics and probability theory?

Statistics is the interpretation and analysis of data to draw conclusions and make decisions. Probability theory is the mathematical study of the likelihood of events occurring. While both deal with collecting and analyzing data, statistics focuses on real-world applications while probability theory is more theoretical and mathematical in nature.

How are statistics and probability theory used in scientific research?

Statistics and probability theory are fundamental tools used in scientific research to analyze and interpret data. They help researchers make sense of their findings, draw conclusions, and make predictions about future outcomes.

What is the importance of understanding statistics and probability theory in everyday life?

Having a basic understanding of statistics and probability theory can help individuals make informed decisions and understand the likelihood of certain events occurring. It can also help in critically evaluating information and making sound judgments.

What are some common misconceptions about statistics and probability theory?

One common misconception is that statistics can always predict future outcomes with certainty. In reality, statistics can only provide probabilities and estimates. Another misconception is that correlation implies causation, when in fact, correlation does not necessarily mean causation.

How can one improve their understanding of statistics and probability theory?

The best way to improve understanding is through practice and application. Engaging in hands-on activities and real-world problems can help solidify concepts. Additionally, seeking out resources such as textbooks, online courses, or working with a tutor can also aid in understanding these complex topics.

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