a summary of the most important content from the statistics 1 course, based on lectures and the book (see below).
Alan Agresti (2018). Statistical Methods For The Social Sciences – 5th global edition. Pearson Education International.
chapter 1 introduction
probability → deductive; how likely is a certain outcome
statistics → inductive; what can we say abt the population
» descriptive: summarizes sample/population data with numbers/tables/graphs
» inferential: generates predictions abt population parameters, based on sample data
rq and data
- population: total group of ppl relevant for the rq
- sample: part of population participating in data collection
reliable reliable reliable reliable
valid valid valid valid
- reliability: consistency of measures
» test-retest: two measurements of the same behavior at different times
» interrater: different observers measuring the same behavior
» internal consistency: interrelation of individual items of a measuring instrument
- validity: how accurately it measures what it’s supposed to measure
chapter 2 sampling and measurement
variable: observed trait that differs between subjects
» behavioral; stimulus; subject; physiological
measurement levels → noir
- nominal: no order in categories
qualitative
- ordinal: order in categories
- interval: equal distance between values
quantitative
- ratio: equal distance and absolute zero
discrete variables: finite set of possible values (whole numbers)
continuous variables: infinite set of possible values (decimals)
problems:
- sampling bias: natural sampling variation
» volunteer sampling → only volunteers as participants
» selection bias → only one type of participant
» under coverage → lack of representation for some groups
- response bias: bad context in which questions (or answers) are given
- non-response bias: unanswered questions resulting in missing data
- sampling error: uncertainty abt just observing a sample
solution? random sampling approach of sufficient size that generates data for everyone approached
1
, sampling methods:
- simple random sampling
» every combination has the same chance of being a sample
» feasible when all participants from the population are approachable
- systematic random sampling
» not every combo has an equal chance 𝑘: skip number
» simple; often good representation of the population 𝑁: population size
» 𝑘 =𝑁/𝑛 𝑛: sample size
- stratified random sampling
» a-priori explicit groups that are compared
» within each group (=stratum) a sample is drawn
» (dis)proportional
o proportional: sampled strata proportions are the same as in the population
o disproportional: sampled strata proportions differ from the population
» useful for comparing different sized groups
- cluster sampling
» not every combination has an equal chance
» useful when it’s unfeasible to approach participants from all clusters
- multi-stage sampling
» multiple sequential stages of random sampling
» combination of the first 4 methods
chapter 3 descriptive statistics
central tendency measures:
∑𝑦𝑖
- mean: 𝑦̅ = 𝑛
- median → middle observation in ordered samples
- mode → most frequent observation
∑(𝑦𝑖−𝑦̅)2
standard deviation: 𝑠 = √ 𝑛−1
» always a positive number
» the greater the variability abt the mean
- sum of squares: 𝑠𝑠 = ∑(𝑦𝑖 − 𝑦̅)2 → (𝑦1 − 𝑦̅)1 + (𝑦2 − 𝑦̅)2 + ⋯ + (𝑦𝑛 − 𝑦̅)2
2 𝑠𝑠
- variance: 𝑠 =
𝑛−1
- standard deviation is the square root of the variance: 𝑠 = √𝑠 2
empirical rule for normal distribution:
- 68% within ± 1𝜎 of the mean
- 95% within ± 1.96𝜎 of the mean
- 99% within ± 3𝜎 of the mean
percentile: 𝑝% of the observations fall below or at that point and (100 − 𝑝)% falls above it
- 25th percentile → lower quartile
- 75th percentile → upper quartile
2
Voordelen van het kopen van samenvattingen bij Stuvia op een rij:
Verzekerd van kwaliteit door reviews
Stuvia-klanten hebben meer dan 700.000 samenvattingen beoordeeld. Zo weet je zeker dat je de beste documenten koopt!
Snel en makkelijk kopen
Je betaalt supersnel en eenmalig met iDeal, creditcard of Stuvia-tegoed voor de samenvatting. Zonder lidmaatschap.
Focus op de essentie
Samenvattingen worden geschreven voor en door anderen. Daarom zijn de samenvattingen altijd betrouwbaar en actueel. Zo kom je snel tot de kern!
Veelgestelde vragen
Wat krijg ik als ik dit document koop?
Je krijgt een PDF, die direct beschikbaar is na je aankoop. Het gekochte document is altijd, overal en oneindig toegankelijk via je profiel.
Tevredenheidsgarantie: hoe werkt dat?
Onze tevredenheidsgarantie zorgt ervoor dat je altijd een studiedocument vindt dat goed bij je past. Je vult een formulier in en onze klantenservice regelt de rest.
Van wie koop ik deze samenvatting?
Stuvia is een marktplaats, je koop dit document dus niet van ons, maar van verkoper d26. Stuvia faciliteert de betaling aan de verkoper.
Zit ik meteen vast aan een abonnement?
Nee, je koopt alleen deze samenvatting voor €4,19. Je zit daarna nergens aan vast.
