Stats Midterm

Statistic

A numerical summary of data

Statistics

Collecting and analyzing numerical data

Population

All of the objects that possess a specific set of characteristics

Sample

Some of the objects that possess a specific set of characteristics

Variable

A characteristic that differs or varies from one individual to another or from one point in time to another

Constant

A characteristic that does not vary from one individual to another or form one point in time to another

Unit of observation

The element that is being studied

Hypothesis

A statement of a relationship between two or more variables

ID

The presumed cause (what I change)

DV

The summed effect or outcome

Control variable

The group that is not manipulated

Experimental group

The group that is manipulated

Continuous measures

Interval and ratio

Categorical measures

Nominal and ordinal, you cannot take the mean of these measures

Case

Unit of measurement

Value

Within each variable makes up the variable (ex. if variable is age then the values are the actual age numbers)

Median

The middle most case in a distribution

Mode

The most frequently occurring value in a distribuion

Mean

The “center of gravity” of a distribution

Skew

Present because of outliers

Positive (tail is on the right)

Negative (tail is on the left)

Kurtosis

Peakedness of distribution (how tall or flat)

Range

The difference between the highest and lowest scores in a distribution

Outlier

Extreme values

Histogram

Way of visually displaying continuous variable (just a frequency distribution)

Frequency distribution

Counts of each thing

Univariate

One variable (ex. Looking at a distribution of income)

Bivariate

Two variables (ex. A comparison)

What are the four levels of measurement and its matching central tendency matches

Nominal- categorical, no distance or numbers (ex. Gender, political affiliation)

Ordinal- categorical, order is known but not the distance between

Interval- ordered, has a true 0, distance between is known, continuous

Ratio- orders, distance between is known, continuous

Mediating variable

Something the explains away the relationship between the IV and DV

Moderating variable

Doesn’t change the relationship between IV and DV but f can have a changing affect on the relationship

Descriptive stats

Describes the study sample

Inferential stats

Used to draw conclusions about a whole/larger s population based on a random sample selected fro the population used

How do outliers skew measures of central tendency such as mean and median

Mean can be pulled up or down but the median will be less affected

What is a bimodal skew?

When there are two humps

What are the percentage chunks for the distribution graph

\-1 and 1 68%

\-2 and 2 95%

\-3 and 3 99%

How do you find your box plot?

You use the interquartile range 25% to 75% or

Find the median and then the medians medians and that is where your boxes are :)

True or false: many real world variables have normal distribution

False

What variable is the outcome?

DV

What measures can you not take the mean of

Categorical (nominal and ordinal)

The Central Limit Theorem

When you take all the little distributions and add them they will always have roughly the same distribution even if some of the ends where different.