Populations and Samples
 

•Population includes all members of a group

–Example: all 9th grade students in America

–Number of 9th grade students at SR

–No absolute number

•Sample

–Used to make inferences about large populations

–Samples are a selection of the population

–Example: 6th period Accelerated Biology

•Why the need for statistics?

–Statistics are used to describe sample populations as estimators of the corresponding population

–Many times, finding complete information about a population is costly and time consuming.  We can use samples to represent a population.

Sample Populations avoiding Bias 

•Individuals in a sample population 

–Must be a fair representation of the entire pop.

–Therefore sample members must be randomly selected (to avoid bias)

–Example: if you were looking at strength in students:  picking students from the football team would NOT be random