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Clemson - STAT 2220 - Class Notes - Week 1

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Section 1: Introduction to Statistics

Stat 2220, Espey

➢ Statistics: the science concerned with the collection, organization, and analysis of information ➢ Statistical literacy: having the skills to question and interpret statistics encountered in everyday life ➢ Unit: the thing being described by a set of data (ex: Clemson Student)

➢ Variable: Characteristic of the units that is measured

➢ Population of units: all units of interest (ex: All Clemson Students)

➢ Population: The variable measurements of the whole population of units

○ N = population size

○ Parameter: A number calculated to describe the population. This is the truth that we want to find, but is usually unknown because most research does not or can not test the entire population of units. ■ μ = population mean

2 =

■ σ population variance

■ σ = population standard deviation Don't forget about the age old question of What are the four main types of psychoactive drugs are?

■ p = population proportion

○ The census attempts to include the entire population of units (All Americans), but inevitably misses some units (eg the homeless)

➢ Sample of units: all units from which data is taken (ex: Clemson students surveyed)

➢ Sample: The variable measurements of the sample of units

○ n = sample size

○ Statistic: A number calculated to describe the sample. This is the best guess at the parameter. ■ x = sample mean If you want to learn more check out Why are bryophytes small plants?

2 =

■ s sample variance

■ s = sample standard deviation

︿ =

■ p sample proportion

➢ Qualitative Data: Is descriptive, categorized, and described by proportions

➢ Quantitative Data: Is numerical with an order of magnitude and described by central tendencies, variance, and deviation

➢ Observational Studies: The variable is measured by observing it in the units Don't forget about the age old question of What are the four leading causes of death that are diet-related?

○ Describes a group or situation

➢ Sample Surveys: A sample of units is surveyed to represent the population of units

○ Nielson Ratings: recorded information about what demographics of people were watching TV ➢ Experiments: Has both an independent (manipulated) and dependent (measured) variable ○ The only method that can imply cause and effect If you want to learn more check out What do percentiles and percentile ranks mean?

○ Independent variable → Dependent variable = Treatment → Response = Cause → Effect

Example 1:

Someone is interested in whether or not registered voters support a particular candidate. 1000 registered voters are asked if they support the candidate

Method:

Survey

Variable:

Opinion of the candidate

Type of Data:

Qualitative

Unit:

A registered voter

Population of Units:

All Registered Voters

Population:

The opinions of all registered voters

Parameter:

The true proportion of yes to no answers of all registered voters ( p )

Sample of Units:

1000 Registered Voters

Sample:

The opinions of the 1000 surveyed registered voters

Statistic:

︿

The proportion of yes to no answers of the 1000 surveyed registered voters ( p )

We also discuss several other topics like How do you draw chair conformations with substituents?

We also discuss several other topics like What do crystalline defects mean?

Example 2:

Someone is interested in finding the average age of all Americans. 1000 Americans were asked for their age.

Method:

Survey

Variable:

Age

Type of Data:

Quantitative (numbers with a magnitude)

Unit:

An American

Population of Units:

All Americans

Population:

The ages of all Americans

Parameter:

The true average age of all Americans (μ )

Sample of Units:

1000 Americans

Sample:

The ages of the 1000 surveyed Americans

Statistic:

The average age of the 1000 surveyed Americans ( x )