Statistics Basic Terms Definition

Definition
Statistics

- science of collecting, organizing, summarizing and analyzing information to draw conclusion or answer questions.
- Provides a measure of confidence in any conclusion

Population

- the collection of all of the people or objects that one considers

Individual

- a single person of object of the population

Sample

- a subject of the population (a group of individual of the population) Descriptive statistics

- describes data through numerical summaries,tables and graphs Example

Inferential statistics

- uses methods that take a result from a sample,extend to the population, and measure the reliability of the result

One wants to conduct a statistics of HWCʼs students on whether they will study outside school. He or she thus then asked 10 students at the school.
Population : All students at the school
Individual : One of the 100 students asked
Sample : 100 students that are asked
Suppose 20 students said they wouldn't study at all outside school.
Descriptive statistics : 80% of the 100 students study outside school
Inferential statistics : It is confident to say that all students at school who would study outside school is 80%

Qualitative
(categorical) variables

- allows for classification of individuals based on some attribute or characteristic

Gender,Zip code

Quantitative variables

- provides numerical measures of individuals
- Arithmetic operations can be performed on the values of a quantitative variable and provides meaningful result

Temperature

Qualitative data

- Observations corresponding to a qualitative variable

Gender(M/F),Zip code(60616,90210)

Definition

Example

Quantitative data

- Observations corresponding to a quantitative variable

Temperature (17ʼC)

Nominal level of measurement - A variable has a nominal level of measurement if it names, labels or categorizes the individual

Gender,Race

Ordinal level of measurement - A variable has a ordinal level of measurement if there is a ranking or ordering

Grade of my GPA

Interval level of measurement - A variable has an interval level of measurement if it makes sense to add and subtract

Price, Temperature

Ratio level of measurement - A variable has a ratio level of measurement if itʼs numerical and it makes sense to divide one by the other to form ration.

Numbers of books of elderly citizens of the numbers of books the entire amount of all citizens Validity

- Represents how close to the true value the measurement is

The use of pH paper or the use of electric pH indicator will results in different acidic value. Reliability

- Represents the ability of different measurements of the same individual to yield the same results

Hawthorne experiment

Explanatory variable

Any variable that explains the response variable. Often called an independent variable or predictor variable.

Response variable

- The outcome of a study. A variable you would be interested in predicting or forecasting. Often called a dependent variable or predicted variable.

Explanatory : Whether people are obsese or not
Response: People consume how many soda Definition

Example

Observational study

- Measures the value of the response variable without attempting to influence the value of either the response or explanatory variables.
- Observes the behavior of the individuals in the study without trying to influence the outcome of the study

- Researchers observe whether people will pay their train fares under the honest system in Minneapolis

Designed experiment

- A researcher assigns the individuals in a study to a certain group,intentionally changes the value of the explanatory variable and then records the value of the response variable for each group.

- Researchers controls different amount of pop to see the relation of it to obesity

Confounding

- Occurs when an explanatory variable that separate the link

Lurking variable: family history

A lurking variable

- An explanatory variable that was not considered in a study, but that affects the vale of the response variable in the study.

Simple random sampling - The chance of every possible sample is equally likely to occur

Drawing sample with a blind-fold on

Systematic sample

- Obtained by selecting every x-th individual from the population

Drawing the most two youngest students of each class.

Cluster Sample

- Obtained by selecting all individual within a randomly selected collection or group of individuals

Convenience Sample

- A sample in which the individuals are easily obtained and not based on randomness

Confounding : people exercise or not

Asking people from my neighborhood to study the amount of electricity use