cogs 14b definitions Flashcards
What is statistics?
quantification and interpretation of variability
Discrete Variables
a variable that takes on distinct, countable values ; giving whole numbers
examples: # of siblings, political party
Continuous Variables
have potentially infinite values between any two observed values
examples: height, weight, interest rates
What are the three levels of measurement?
Nominal, Ordinal (ranked), Interval/Ratio
Define Nominal data fa me?
variables that have two or more categories, but which do not have an intrinsic order
examples: sex, blood type, favorite kpop group
Define Ordinal (ranked) data fa me?
a set of categories that are organized in and ordered or ranked sequence ; possesses an inherent order
examples: letter class grades, clothing size
Define Interval/Ratio data fa me?
- used to measure variables with equal intervals between values
~ interval has no true zero point while ratio does
~ quantitative
interval example: IQ score, GPA
ratio example: distance, weight, income
Population
Complete collection of observations or potential observations
for all individuals or units of interest
Sample
A partial set of observations taken from the population
Convenience sample
respondents from a population that can be conveniently
contacted/accessed by the researcher
examples: from a poll, survey, people in crowded locations
Parameter
value reflecting something in the entire population of interest
Statistic
a value that reflects something from a sample (can be estimate
of population parameter)
Random sampling
all potential observations in the population have an
equal chance of being selected in a sample
Sampling error
samples can be unrepresentative of the whole population to varying degrees and this causes errors of varying sizes based on level of representativeness - due to this, sample statistics will
vary by chance
Descriptive Statistics
Provides description of data collected
- Approaches presentation of data in a digestible manner
- How can we organize the sample data?
- Measures of central tendency and variability, mean, median, mode
Inferential Statistics
Helps figure out how sample of data will generalize
- Makes inferences and estimates using data
- Hypothesis testing, confidence intervals, regression analysis, ANOVA
- What does the sample data say about the population?
Bar Charts
when is best used?
- Best used when x-axis var is discrete and nominal
- Used for presentation of summary stats or raw data
- Differences easy to see
Line charts
what is best used for and useful for indicating?
- X-axis variable is continuous and interval/ratio (quantitative data)
- Useful for indicating trends over time
Scatter Plots
best used for what kinda data and what kind of values?
- Best used when both x and y coordinate values are interval/ratio scale
- best used for bivariate data ; used in observational studies with no independent variables
- X & Y coordinates represent values of 2 diff variables
Frequency distributions
sorting observations into classes and displaying the number of occurrences in those classes
(can be shown using a histogram or table)
Ungrouped frequency
distribution
- distribution that displays the frequency of each individual data value instead of groups of data values
- best to use when you have less
than 20 single-value classes
Grouped Frequency Distribution
only possible with what data? and what does it organize?
- organizing a large set of data into classes with more than 1 value
- only possible with ordinal and interval/ratio data
- even if a group has 0 observations, it is included
- choose appropriate bins based on # of observations
Outliers
extreme scores or observations - they lie at the far edge of the frequency distribution and are extremely unlike rest of the sample
Relative frequency (f) distributions
what does it display? and it’s helpful when…?
- display the frequency of each class as a proportion
- helpful when discussing ratios
- distribution that shows the proportion of the total number of observations associated with each value or class of values