A Little Probability

Probability is one of the foundations of statistics courses, in that you are constantly evaluating the likelihood of something. The key to probability is imagination. You have to imagine the scenario , given the facts in your word problem. Become one with the facts….Here is a good example to illustrate what I am talking about…

Scenario: You have 52 playing cards

Probability (Event #1): Probability of pulling a 2 of hearts out of the deck: 1/52

Probability (Event #2):Probability of pulling an Ace: 1/52*4=4/52

Probability of the event =             Number of favorable outcomes
Total number of possible outcome


You have 52 total number of possible outcomes in your scenario.  The likelihood for pulling any card out of the deck is 1/52. Why? Because each card has an equal probability of being chosen before you consider any specific scenario.  Any one of those cards can show up when you draw a card. The “number of favorable outcomes” represent the probability of your event occurring  when a card is drawn. For Event #1,  any regular card player will recognize that a deck only has one card with the  2 of hearts.  For event  #2, You have four aces in the deck.

As a side note, have you ever heard of the phrase ‘with and without replacement’? Translation: If I choose a card out of a deck with replacement, that means the card is still ‘in play’ in terms of total number of possible outcomes. If I choose a card out of a deck without replacement, the card is no longer in play and not part of the possible outcomes.

If you enjoyed this blog there are more to follow..-Amy

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