Research Modules

Types of Psychological Research Questions

2.eg. Is anxiety related to depression?

The goal of psychological research

We’re trying to make inferences about a population

• population: everyone of interest to a research question

Samples

Group of ppl drawn from population that participate in exp - measurement of sample allows us to make inferences abt population

• is what is typical in samples typical for population?

Which scores are an indicator of what’s typical?

mean scores

• population mean and sample mean can be compared to assess difference

Distributions of data

constructs take on diff values for diff people in a sample

• collectively, all scores tgt creates distribution of data

• distribution of data can be described in terms of central tendency and variability

Graphic way to represent distribution of data

histogram

‘normal’ shape

Bell curve

What does ‘typical’ mean?

expected

• eg. extreme scores are infrequent and

Typical vs extreme

In a normal distribution, approx. 95% of scores fall within 2 SDs of mean

• that 2 SDs mark is called the ‘critical limits’

• anything outside of this is extreme (top and bottom 2.5%)

Applying the 2s rule

How to find out if an entire sample is typical of the population?

Use the distribution of sample means

Distribution of sample means

It’s a theoretical distribution governed by a mathematical theorem called the central limit theorem

Central limit theorem

tells us the precise characteristics of the distribution of any distribution of sample means

What central limit theorem tells us

How do we use central limit theorem and sample means?