PSYC1040 Week 5 Flashcards
Variability, situational factors and normal distribution
1
Q
Variability
A
- most studies involve taking measures of a sample of participants drawn from a population
- but, any sample distribution will likely differ from the population distribution, just by change, so individual studies will not be perfectly reliable
- in particular, each sample mean will differ from the population mean
- assuming the population distributions is normal, we can estimate how much a sample mean will likely differ from a population mean, if we know two things:
~ the n.o of participants in a sample
~ the amount of variability in the population (SD).
2
Q
Stable individual differences
A
- basically, traits of participants
3
Q
Situational factors
A
- e.g background noise during a testing session, participants experiences on the day of testing and soon
- to quantify the extremity of a score, we can say how many SD it lies from the mean
4
Q
The normal distribution - characteristics
A
- many variables are normally distributed e.g height, IQ, personality measures, memory performance, symptom severity etc
- when variation is due to many separate random influences, it will tend to follow a normal curve
- many inferential statistical tests are therefore based on the properties of a normal distribution
- in particular, they’re based on the mapping of z-scores to percentiles in a normal distribution