Statistics Exam 1

Data

Specific info of the individuals

Two types of data:

Quantitative and Qualitative

Quantitative data

numeric

Qualitative data:

Non-numeric or categorical

Two types of Quantitative data

Discrete and Continuous

Discrete

whole numbers, gaps between values

Continuous

decimals, no gaps

Observed studies

Change come variables to see the effect in other variables

Explanatory variables

“cause”

Response variables

“effect”

Lurking variables

Variables not considered which are having an effect on other variables

Frequency

how many of each data value?

Relative Frequency

What proportion if each data values?

Types of samples

Simple Random

Cluster

Systemic

Stratified

Convenience

Simple random

Randomized for each individual

Cluster

A randomized subgroup is the sample

Systemic

Every kth individual is in the sample

Stratified

A random sample from each group

Convenience

Less randomness but easier to create

Types of Bias:

Sample Bias

Non response Bias

Response Bias

Sample Bias

The sample does not represent the population

Non-response bias

Not everyone competes the survey

Response bias

The data doesn’t represent the sample.

Mean Notation in a sample

x̄

Mean notation in a population

μ

Standard deviation notation in a sample

S

Standard deviation notation in a population

σ

A statistic is resistant/resilient

Mean is not resistant, Median is

What kind of graph is this?

Histogram

What kind of graph is this?

Boxplot

What kind of graph is this?

Bar graph

What is the mean?

The average of all of the data

What is the median?

The middle number of the data

Is this negatively or positively associated, What is the slope of regression, What is the linear correlation coefficient?

Positively associated, Slope of regression line is positive, Line correlation coefficient is r= +1

Is this negatively or positively associated, What is the slope of regression, What is the linear correlation coefficient?

Negatively associated, Slope of regression is negative, Line correlation coefficient is r= -1

Outlier equations

…less than Q1-1.5IQR

….more than Q3+1.5IQR

Variance

A measure of dispersion

Standard deviation

The square root of the variance

IQR

Inter Quartile Range, a measure of dispersion, IQR=Q3-Q1

Outliers

Data values separated from the rest if the data.

Quartiles

The quartiles mark the 25 and 75% spots in the data just like the median is the 50% mark. The first quartile is the 25% mark “Q1”. The third quartile us the 75% mark “Q3”.

Example of simple random Sampling

Putting names into a hat

Example of Cluster sampling

having high schoolers fill out a survey

Example of a systemic sample

select every 10th person coming into a store.

Example of a stratified example

dividing people by grade then surveying people from each group

Example of convenience sampling

A teacher surveying their own students.