AP Statistics › How to identify independent events
True or False: When 2 cards are drawn without replacement from a regular deck of 52 cards, the event of drawing a heart first independent of the event of drawing a heart second.
False
True
Cannot be determined by the information given.
Sometimes
These events are not independent, because if one event happens, it affects the probability of the other event happening. Consider the probability of drawing a heart and the probability of getting a heart given a heart was already drawn. If these two probabilities are the same, the events are independent. If the two probabilities are not the asme, the events are not independent.
After a heart has already been drawn, there are now only 52 cards total and 12 hearts left. These two probabilities are not equal, therefore the events are not independent.
True or false:
A family has 3 boys. The probability that the fourth child will also be a boy is less than 50%
False
True
More information is needed.
Sometimes
The gender of each child can be considered an independent event. Each child has a 50% chance of being a boy, and whether a boy was already born previously does not affect the next child's gender.
True or false: When drawing two cards with replacement, the event drawing a spade first is independent of the event drawing a heart second.
True
False
Sometimes
More information is needed.
These two events are independent of one another. During sampling with replacement, the first card does not affect the second card being picked.
To illustrate, consider the probability of drawing a heart first
Assuming you first drew a heart and replaced it in the deck, does the probability of drawing a heart as the second card change?
The probability remains the same, there are still 13 hearts and 52 total cards.
Events and
are known to be independent.
while
. What must
be?
Because the two events are known to be independent, then the following is true by definition.
.
This then becomes an algebra problem:
Each answer choice describes two events. Which of the following describes independent events?
A coin is flipped in the air and the result is heads. The coin is flipped in the air again.
A card is drawn from a pile and set aside. A second card is drawn.
One of ten differently colored candies is selected from a jar and eaten. A second candy is then randomly selected.
A shirt is randomly selected from a drawer and is placed in the laundry. A second shirt is randomly slected from the drawer.
A marble is randomly drawn from a bag and set aside. A second marble is drawn from the bag.
Two events are independent of each other when the result of one does not affect the result of the other. In the case of the coin being flipped, the first result in no way influenced the result of the second coin flip. In contrast, when a card is removed from a deck of cards and set aside, that card cannot be selected when a second card is taken from the deck.
Mary randomly selects the king of hearts from a deck of cards. She then replaces the card and again selects one card from the deck. The selection of the second card is a(n)_________ event.
independent
dependent
The selection of the second card is an independent event because it is unaffected by the first event. If the king of hearts had not been replaced, then the probability of selecting a particular card would have been affected by the first event, and the second selection would have been dependent. This, however, is not the case in this question.
True or false: Two events which are mutually exclsuve are also independent events.
False
True
Sometimes
More information is needed.
Events which are mutually exclusive are dependent events. This is becauce if one event happens, it affects the probability that the other event will happen.
Example- Tonight you may attend a soccer game or a basketball game. These events are mutually exclusive because they share no overlap. However, if you go to the basketball game, it changes the probability of you going to the soccer game to zero. Therefore, mutually exclusive events are not independent.
What is the probability of getting a sum of when rolling two six-sided fair dice?
The sample space, or total possible outcomes, when rolling two six-sided dice is .
Ways to get what you want:
So there are ways to get a
.
So the probability becomes
A bag is set in front of you with three different colored marbles inside. There are 9 red marbles, 10 blue marbles, and 7 yellow marbles. What is the probability that you draw a marble that is not yellow?
First you find the total amount of marbles that are in the bag which is 26 (). Then you must add up all of the marbles that are not yellow which is 19 (9 red marbles + 10 blue marbles). Finally, you must divide the total marbles that are apart of you set (19) by the total marbles (26) and that gives you a probability of
.
Given a pair of fair dice, what is the probability of rolling a 7 in one throw?
1/6
1/2
1/3
1/4
5/6
There are 36 total outcomes for this experiment and there are six ways to roll a 7 with two dice: 1,6; 6,1; 2,5; 5,2; 3,4; and 4,3. Thus, 6/36 = 1/6.