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# Valid discrete probability distribution examples

AP.STATS:
VAR‑5 (EU)
,
VAR‑5.A (LO)
,
VAR‑5.A.1 (EK)
,
VAR‑5.A.2 (EK)
,
VAR‑5.A.3 (EK)
CCSS.Math:
Worked examples on identifying valid discrete probability distributions.

## Want to join the conversation?

• The second example includes the statement "Each creature has an equal probability of getting selected", yet the three answers are not equal. What gives? • Although the wording is confusing, I believe it means that the "picker"/"space alien" is not more bias towards any type of creature, so it will not purposefully choose a chicken, cow, or human over any other type of creature. Or in other words, the space alien is picking its creatures at random. But that doesn't mean the probability that it picks a chicken is equal to the probability that it picks a cow, because there are a lot more chickens than cows in the example. Another example that might clear things up would be: you randomly pick a red or blue marble out of a bag. The bag contains 10,000,000 red marbles, and 1 blue marble. What is the probability of picking a blue marble?
• It seems that “Valid discrete probability distribution examples” video should be before “Practice: Probability models”, not after. • Just because you are given a probability problem, does not mean that you could actually solve it. Ensuring it is a valid probability model proves that:

There is a total 100% chance of anything happening at all
Prove whether it is dependent or independent
Find sampling errors. for instance:
if there is a 30% chance of selecting a green marble, 40% chance of selecting a blue marble, and 40% chance of selecting a yellow marble we know this is impossible, or that information is being withheld
(1 vote)
• in the first example, it says that all scenarios must be equal to 100% (and positive). How was the second example's answer, 221, equal to a hundred percent? • This should come before probability models (practice).
(1 vote) • in the first example it is necessary too to check if all possibilities are displayed. if not all possibilities displayed so it is reasonable that the sum of the percentages of the displayed probabilities dont add up a whole one or 100%.
would anyone argue this!
(1 vote) • "Each creature has an equal probability of getting selected", can there be an unequal probability of getting selected here? ex: alien is 20% more likely to pick a cow (biased reason), how will this change the answer?
(1 vote) • What happens when a probability model has total outcomes greater than 100%?
(1 vote) • what is the random variable in the alien case?
(1 vote) 