Sampling, Comparing Data, and Probability
Aligned to 7.SP.C.5 — Common Core State Standards for Mathematics.
What this lesson teaches
Probability is a number from 0 to 1 that tells how likely something is, where 0 means impossible and 1 means certain. For equally likely outcomes, it equals the number of favorable outcomes divided by the total. A random sample lets you estimate facts about a whole group.
Worked examples
Example 1
A bag has 2 red and 3 blue marbles, 5 total. The probability of drawing red is 2 out of 5, or 2/5.
Example 2
Roll a fair die. P(even) = 3/6 = 1/2, because 2, 4, and 6 are the three even faces out of six.
Example 3
Probability is always between 0 and 1. P = 0 means impossible, P = 1 means certain; an answer of 5/3 means something went wrong.
Practice questions
- What is the probability of rolling a 4 on a fair die?
- If a probability is 0, what does that mean?
- A spinner has 4 equal parts, one green. What is P(green)?
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Muestreo, Comparación de Datos y Probabilidad
La probabilidad es un número del 0 al 1 que indica qué tan probable es que ocurra algo, donde 0 significa imposible y 1 significa seguro. Para resultados igualmente probables, es igual al número de resultados favorables dividido entre el total. Una muestra aleatoria te permite estimar características de todo un grupo.
Ejemplo 1: Una bolsa tiene 2 canicas rojas y 3 azules, 5 en total. La probabilidad de sacar una roja es 2 de cada 5, o 2/5.
Ejemplo 2: Lanza un dado justo. P(par) = 3/6 = 1/2, porque 2, 4 y 6 son las tres caras pares de seis.
Ejemplo 3: La probabilidad siempre va de 0 a 1. P = 0 significa imposible, P = 1 significa seguro; una respuesta de 5/3 significa que algo salió mal.
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