PSYC1040 Week 5

Question 1

Variability

Answer 1

• 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).

Question 2

Stable individual differences

Answer 2

• basically, traits of participants

Question 3

Situational factors

Answer 3

• 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

Question 4

The normal distribution - characteristics

Answer 4

• 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