OCR MEI Statistics 1

What is a "discrete set of data"?
A set of data that can only take on particular values.
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Example:
When rolling 2 die and adding the results together, the total cannot be 2.5 or 100. Because the die are fair, the result will be random. It is variable because the scores can vary.
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Discrete probability distribution
Work out the possible scores that can be rolled. Find the of the score being each of these ((Summation of P(X=x))=1). Draw a stick graph, this shows how the probabilities are distributed.
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What is E(X)?
It is effectively the mean of the distribution. It is the value on average we would get after a long long time.
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What is the formula of E(X)?
Summation of xP.
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What 3 types of data skew can we get?
Positive, negative and symmetrical.
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Symmetric stick graphs=...?
No skew. As a consequence, E(X)=median.
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Stick graph with its tail to the left of the data is a ... skew?
...=negative.
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A tail to the right of the data on a stick graph has a ... skew?
...=positive.
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What is variance for?
When the frequencies are probabilities instead.
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Formula for Var(X).
(Summation of x^2*P)-E(X)^2 = E(X^2)-E(X)^2
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E(X) and Var(X) of B(n,p)
For a B(n,p): E(X)=np and Var(X)=np(1-p)=npq
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Card 2

Front

Example:

Back

When rolling 2 die and adding the results together, the total cannot be 2.5 or 100. Because the die are fair, the result will be random. It is variable because the scores can vary.

Card 3

Front

Discrete probability distribution

Back

Preview of the front of card 3

Card 4

Front

What is E(X)?

Back

Preview of the front of card 4

Card 5

Front

What is the formula of E(X)?

Back

Preview of the front of card 5
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