stats

cognitive reflection test

questions have a quick answer that comes to mind, but is often wrong

phenomena

observable facts or events

constructs

not directly observable (ex. personality, intelligence, etc)

what do we use variables for in research?

to represent constructs or phenomena

operationalization

turning phenomena and constructs into variables

example of operationalism

• satisfaction with life scale

• single question

• cantril’s ladder

• experience sampling

ways that operationalization varies

• validity

• convenience vs depth

• measurement error

• generalizability

kinds of variables

• categorical

• numeric

• ordinal

categorical variable

finite set of values with NO meaningful order

numeric

values ordered from less to more; gaps mean the same everywhere

ordinal variables

meaningful order, but with unequal gaps between values

discrete numeric variables

whole numbers

continuous numeric variables

any value

standard deviation

distance from the mean; average of the average

bell curve/normal distribution

• mean = median

• 2/3 of observations are within 1 SD of the mean

• symmetric graph used in stats to show how data is spread out

skewed distribution

peak of bell curve is not central; pulls mean towards the tail

4 main types of curve/scale

• roughly symmetric

• left skewed

• right skewed

• pile at zero, then long tail

population

EVERYONE we want to make a claim about

sample

people actually measured

census

attempt to measure everyone

parameters

number describing entire population; fixed value

statistic

number describing your sample; change sample to sample

μ (mu)

mean of full population (parameter)

σ (sigma)

standard deviation of full population (parameter)

x̄ (x-bar)

mean of sample (statistic)

s

standard deviation of sample (statistic)

4 types of samples

• random

• stratified

• convenience

• snowball

random sample

everyone in population has equal chance of getting picked

stratified sample

random, but within groups (each group has equal chance of getting picked)

convenience sample

whoever is easiest to reach or volunteers

snowball sample

participants recruit people they know

sampling variability

different samples of the same populations have different statistics