Module

Question 1

The Goal of Psychological Research

Answer 1

• When we conduct a psychological research project, our aim is to make inferences (in other words, suggestions or claims) about a population. Put simply, we want to say something about a population.
• A population is everyone of interest to a
research question. In other words, it is the
research question that defines the population.

Question 2

Making Inferences Based on Samples

Answer 2

It is usually not possible to recruit all people in a
population to participate in a study. That’s okay, we
can instead use a sample: a group of people taken
from the population to participate in a study.
We can then make inferences about the population
based on what happens with measurement of our
sample. We aim to infer that what is typical for our
sample should also be typical for the population.

Question 3

Distributions of Data

Answer 3

To understand a psychological construct, we need to
know how it is distributed across a population.
When measured, constructs takes on different values for
different people in a sample.
Collectively, those different values form a distribution of
data, which can be described in terms of central tendency
and variability.

Question 4

The Normal Distribution

Answer 4

Majority of
observations are
in the middle.
Observations
reduce in
frequency towards
the tails.
The distribution is
symmetrical.

Question 5

The 2s Rule of Thumb

Answer 5

In a distribution with a normal shape, 95% of scores fall within approximately 2 standard deviations (s) of the mean.
m= mean, s= standard deviation
Lower limit= m-2s
upper limit= m+2s

Question 6

One Population, Many Samples

Answer 6

When we conduct
research, we usually
recruit one sample
from each population of
interest.
However, there are
many samples that
could possibly be
recruited from any
population
Firstly, we would need a score for our one sample.
This would be the sample mean. Next, we would
need a distribution made up of sample means,
within which, we could examine our one sample
mean

Question 7

Central Limit Theorem

Answer 7

The precise characteristics of a distribution of
sample means for samples of any size (n).
The mean of the distribution of sample means is
the same as the population mean.
For large sample sizes (30 or more), the
distribution of sample means will have a normal
shape.
The standard deviation of the distribution of
sample means, which is called “Standard Error”.
The standard error formula: σM = standard error/ square root of n
__
As sample size increases, standard error
decreases. In turn, estimation of the population
mean becomes more precise. When a sample is
large enough, its mean provides a reliable estimate
of the population mean.