This document discusses independent and repeated samples in studies. Independent samples come from completely separate groups, like students in different grades since one cannot be in multiple grades at once. A study can also have both independent samples, like testing students in different grades, and repeated samples, such as testing the same group of students in multiple grades at the beginning and end of a course to compare results over time within the same analysis.

1. Independent samples are samples from groups that are completely separate from one
another.
Sometimes a study can have both independent and repeated samples
4 Levels of Independent Samples 9th 10th
Independent Variable
One cannot be in grade 9, grade 10, grade 11, or grade 12 at the same time; therefore, samples
of from each of these groups are independent from one another.
4 Levels of Independent Samples
Independent Variable
2 levels of Repeated Samples
A group of 9th, 10th, 11th, and 12th graders are tested at the beginning and at the end of the course.
In this way we can compare them with each other and over time all in the same analysis.
12th
Year in School
11th
Pre-
test
9th 10th 12th
Year in School
11th
Post
test
Time
Pre-
test
Post
test
Pre-
test
Post
test
Pre-
test
Post
test
Time Time TimeIndependent Variable