Biostats exam 1

Nominal Data

Putting observations into a category

Qualitative Data

consists of words or codes that represent a category

Ordinal data

Put ranks observations compared to one another

Ranked Data

consists of numbers that indicate order/standing

Ratio/interval data

puts observations on a scale with a true zero and equal intervals

Quantitative data

numbers that indicate an amount or count of something

Descriptive statistics

Summarize data, true fact of the given dataset

Inferential statistics

Uses a small sample to estimate something about a big population

What kind of testing uses Inferential statistics

Hypothesis

Independent Variable

a group, treatment, condition, or other situation that is manipulated by the experimenter

Dependent variable

something believed to be influenced by the independent variable(s)

Confounding variable

a variable that the experimenters have failed to account for that compromises the interpretation of a study

Population

An entire, comprehensive group

Sample

a subset of the population, typically used to infer things about the population

Sampling

Random samples are not casual or haphazard, getting truly random samples requires care

Random sampling

is used when surveying, to obtain a “snapshot” of the population

Random assignment

is a process used in an experiment to minimize bias in your experimental groups

Number of observations symbol for a sample

n

Number of observations symbol for a population

N

Mean symbol for a sample

x̄

Mean symbol for a population

μ

Variance symbol for a sample

SD²

Variance symbol for a population

σ²

Central tendency

Middle of the data set

Variability/ dispersion

How spread out a dataset is

Mean

Common average

How to calculate mean

The sum of all observations, divided by the number of observations

Median

Splits the dataset into two halves of equal size

Mode

The most common value(s) in a dataset

Standard deviation symbol for a sample

SD

Standard deviation symbol for a population

σ

Robust

Can tolerant without losing value

what type of data is mean most popular for

Interval/ ratio data

what type of data is median most popular for

Interval/ ratio and ordinal data

what type of data is mode most popular for

Nominal and ordinal data

Data can almost always be what

Demoted

Data can never be what

Promoted

What are examples of descriptive statistics

Counts, central tendency (average), variability, correlation

What does inferential statistics depend on?

the quality of the input

WHat is inferential statistics separated into

Parametric and non-parametric

What are examples of inferential statistics?

t-tests and ANOVA

Negative skew

a lot of negative data, left side

Positive skew

a lot of positive, right side

Biomodel

2 modes, 2 populations, 2 curves laid on top of each other

Binning

0-100 to ordinal scale, ‘putting in a bin’

Variability

give us a unique definition of our distribution, whats weird about it

Range

the simplest measure of variability

How to calculate range

the difference between the largest and smallest values

Sum of squares

a measure of variability, but we rarely use it on it’s own

How to calculate standard deviation

The square root of the variance

What STVDEV calculation does SSPS use

Sample Standard Deviation

Standard deviation

a normalized measure of how widely distributed a dataset is

3 rules of standard deviation

• The majority of scores/samples appear within one standard deviation

• A moderate amount of scores deviate by 1-2 standard deviations 

• Few scores deviate more than two standard deviations 

Standard Normal curve

Mean of 0, % is # observative

What is with in 1 STVDEV

68% of the data closest to the mean

What is with in 2 STVDEV

27% of the data closest to the mean

What is with in 3 STVDEV

5% of the data closest to the mean

Interquartile of Range

The range of the middle 50% of scores

Why is interquartile range useful

Not affected by outliers, a good measure of variability when several or extreme outliers are present

Frequency count

Counting how often it shows in data

Cumulative percent

Frequently and above

Cumulative count

Cumulative percent to numbers