AP Statistics

Simple random sample

1. Label individuals or items

2. random number generator to decide

3. Select invididuals

A fair unbiased way to decide those who will be chosen

Convenient sample

when individuals are selected because they are easy to find or are readily available to the researcher, high bias

Voluntary response

A survey that mainly people who feel strongly one way or the other will answer, it can lead to high bias.

Population

Individuals we want to sample

Low bias

A fair sample method that allows every group of the population is properly represented

low variability

when dots are plotted very clustered together

Stratified random sample

A sampling method where the population is divided into homogeneous subgroups (strata), and then a simple random sample is drawn from each subgroup

Homogeneous

when items being sampled are very similar or uniform to each other making it easy to draw better results from

Heterogeneous

a population that is very diverse and different significantly in characteristics or traits

cluster sampling

breaking the population into clusters and sampling the entire cluster, example of heterogeneous grouping.

Systemic sampling

selecting individuals that involves selecting members based on regular intervals

undercoverage bias

certain groups of the population that are underrepresented or are missing in the sample

Non response bias

when people don’t respond to the survey, leading to bias

response bias

when the people responding are providing inaccurate answers or the questions wording is strange

confounding variable

an external or uncontrolled factor in an experiment that’s related to the indapendent variable and the dependent variable, an example of this is diet in a study between weight loss and exercise

Explanatory variable

It is the input in an experiment, the cause for the effect an example is exercise in an experiment between exercise and weight loss

Response variable

Dependent variable, based on the explanatory variable in an experiment, so it would be the weight loss in exercise and weight loss

observational study

a study where there are no treatments imposed

experimental study

a study where there are treatments imposed