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### Course: Praxis Core Math > Unit 1

Lesson 3: Statistics and probability- Data representations | Lesson
- Data representations | Worked example
- Center and spread | Lesson
- Center and spread | Worked example
- Random sampling | Lesson
- Random sampling | Worked example
- Scatterplots | Lesson
- Scatterplots | Worked example
- Interpreting linear models | Lesson
- Interpreting linear models | Worked example
- Correlation and Causation | Lesson
- Correlation and causation | Worked example
- Probability | Lesson
- Probability | Worked example

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# Random sampling | Lesson

## What are random samples?

A provides information about a without having to survey the entire group.

To make valid conclusions about a population, we need a sample that recreates the characteristics of the entire population on a smaller scale.

A good sample is representative and random.

**Representative**means that the sample includes only members of the population being studied.**Random**means that every member of the population being studied has an equal chance to be selected for the sample.

### What skills are tested?

- Identifying a valid sampling method
- Determining the population for which the conclusions of a sample are valid
- Using a random sample to make an estimate

## What are some bad ways to sample?

**Sampling method**refers to how participants are selected for a sample.

*Bad*sampling methods include those that:

- Gather data from outside the population being studied
- Gather data that overrepresent or underrepresent a subgroup of the population (not random)

## What population can we make inferences about using data from a sample?

We can make inferences about

*only*the population from which the random sample was selected.## How can we use sample data to make an estimate?

We can use data from a random sample to estimate the number in the population having a particular attribute.

To make an estimate, we need to know the and the population size.

## Your turn!

## Things to remember

A is a way to gather information about a without having to survey the entire group.

- A good sample must be both and !

We can use the results of a good sample to make estimates about the population it was drawn from.

$\text{estimate}=$ $\text{population size}\times \text{sample proportion}$

- Estimates are valid
*only*for the specific population the sample is drawn from!

## Want to join the conversation?

- Is anyone else doing it backwards?

Instead of 600 multiplied by 6/50 = 72, I simplify the fraction and write it as 600 divided by 25/3 = 72. Same answer, different formula.(1 vote) - This is so confusing(0 votes)
- It makes sense(0 votes)
- Why different scoring for praxis VA math sub test and core praxis math test?(0 votes)