Basic Probability
What is the probability of flipping a coin and getting heads?
1/2
What is an "outcome" in probability?
A possible result of an experiment.
A spinner with 4 equal parts numbered 1-4, what is the probability of landing on 3?
1/4
Which is more likely: rolling a 2 on a die or flipping tails on a coin?
Flipping tails (1/2) is more likely than rolling a 2 (1/6).
What is theoretical probability?
Probability based on all possible outcomes.
If the chance of rain is 70%, what is the probability it won’t rain?
30% or 0.30
A bag has 3 red marbles and 2 blue marbles. What is the probability of picking a red marble?
3/5
Define "event" in a probability context.
One or more outcomes from an experiment.
What is the probability of rolling a number greater than 4 on a six-sided die?
2/6= 1/3
If chance of winning is 1/4 and losing is 1/2, which is more likely?
Losing, 1/2 > 1/4.
What is experimental probability?
Probability based on the actual results of an experiment.
A class has 10 boys and 15 girls. Probability of picking a girl?
15/25 = 3/5
What does it mean if an event is "impossible"? Give an example.
Probability 0;
Example: rolling a seven on a six-sided die.
What is the difference between "likely" and "unlikely" events?
Likely > 1/2, unlikely < 1/2.
Jelly beans: 5 green, 3 yellow, 2 purple. Probability of yellow?
3/10
Two events have equal probability. What does this mean?
Both are equally likely to happen
A spinner theoretically lands equally on 4 colors. You spin 40 times and get red 5 times. What’s the experimental probability of red?
5/40= 1/8
Probability of picking a heart from a deck of cards?
1/4
A jar contains 4 green, 5 white, and 1 black marble. What is the probability of picking a marble that is not white?
4+1/10= 5/10= 1/2
What is a "sample space"?
The set of all possible outcomes.
A box has 6 blue pens, 4 black pens, and 5 red pens. Probability of picking a red or black pen?
4+5/15= 9/15= 3/5
Which is more likely: picking a heart from a deck or rolling a 6 on a die?
Both have a probability 1/4 (hearts) vs. 1/6 (rolling a 6), so picking a heart is more likely.
Explain why experimental and theoretical probabilities might be different.
Experimental probability depends on actual trials and may vary; theoretical is based on all possible outcomes.
A weather forecast says there’s a 40% chance of snow. What is the probability it does not snow?
60% or 0.6
If you toss two coins at the same time, what is the probability that both coins land on heads?
1/2 x 1/2 = 1/4
What is a "simple event"?
An event with only one outcome.
You roll two six-sided dice. What is the probability the sum is 7?
There are 6 favorable pairs (1+6, 2+5, 3+4, 4+3, 5+2, 6+1) out of 36 total outcomes. Probability:6/36= 1/6
Event A has probability 3/8 and event B has probability 5/8. Which event is more likely, and by how much?
Event B is more likely by 5/8−3/8=2/8=1/4.
Explain why experimental and theoretical probabilities might be different.
Experimental probability depends on actual trials and may vary; theoretical is based on all possible outcomes.
A jar contains 8 red, 6 green, and 6 blue candies. If you pick one candy without looking, what is the probability it’s either green or blue?
6+6/20= 12/20= 3/5