1.1 / 1.2 Stats

Statistics

Science of collecting organizing analyzing and interpreting data

Science of collecting organizing analyzing and interpreting data

Statistics

Purpose of statistics

Use data to answer questions

Use data to answer questions

Purpose of statistics

Population

Entire group of interest

Entire group of interest

Population

Population example

All registered voters in Washington

All registered voters in Washington

Population example

Big picture group in a study

Population

Sample

Smaller group from a population

Smaller group from a population

Sample

Sample example

250 students from a college

250 students from a college

Sample example

Group used to represent a population

Sample

Why use a sample

Population is usually too large to survey

Population too large to survey

Why use a sample

Parameter

Numerical measurement of a population

Numerical measurement of a population

Parameter

Parameter describes which group

Population

Population measurement

Parameter

Parameter symbols

μ σ p

μ σ p

Parameter symbols

True value for the whole group

Parameter

Usually unknown population number

Parameter

Statistic

Numerical measurement of a sample

Numerical measurement of a sample

Statistic

Statistic describes which group

Sample

Sample measurement

Statistic

Statistic symbols

x̄ s p̂

x̄ s p̂

Statistic symbols

Number calculated from collected data

Statistic

Population goes with

Parameter

Parameter goes with

Population

Sample goes with

Statistic

Statistic goes with

Sample

Simple Random Sampling

Every possible sample has equal chance

Every possible sample has equal chance

Simple Random Sampling

Abbreviation for Simple Random Sampling

SRS

SRS stands for

Simple Random Sampling

Student IDs chosen by random generator

Simple Random Sampling

Random selection of individuals

Simple Random Sampling

Systematic Sampling

Select every kth individual

Select every kth individual

Systematic Sampling

Survey every 20th customer

Systematic Sampling

Pattern of every kth person

Systematic Sampling

Stratified Sampling

Divide into groups and sample from each group

Divide into groups and sample from each group

Stratified Sampling

Another name for groups in stratified sampling

Strata

Strata means

Groups within a population

Freshmen sophomores juniors and seniors sampled separately

Stratified Sampling

Goal of stratified sampling

Represent every group

Cluster Sampling

Divide into clusters and survey entire selected clusters

Divide into clusters and survey entire selected clusters

Cluster Sampling

Randomly choose classrooms and survey everyone inside

Cluster Sampling

Survey everyone in selected groups

Cluster Sampling

Goal of cluster sampling

Survey entire chosen clusters

Convenience Sampling

Survey easiest people to reach

Survey easiest people to reach

Convenience Sampling

People in student union surveyed because they are nearby

Convenience Sampling

Major problem with convenience sampling

Often biased

Often biased

Convenience Sampling problem

Biased results are

Misleading results

Misleading results

Biased results

Population versus sample

Entire group versus smaller group

Parameter versus statistic

Population measurement versus sample measurement

Population symbols

μ σ p

μ σ p belong to

Population

Sample symbols

x̄ s p̂

x̄ s p̂ belong to

Sample

True number for a population

Parameter

Calculated number from a sample

Statistic

Qualitative data

Categorical information Quantitative data