L3: Experiments & Quantitative Research Methods

What is the first step in the psychological research process?

Theory development

What is a research hypothesis?

A general statement about how we think the world works based on observations or prior knowledge.

What are independent variables (IV) in an experiment?

Factors that you manipulate or control to observe their effect on the dependent variable.

What are dependent variables (DV) in an experiment?

The outcomes or responses you measure that are expected to change due to manipulation of the independent variable.

What is a nuisance variable?

Factors that can influence the relationship between independent and dependent variables if uncontrolled.

What is experimental control?

Methods used to minimize the influence of nuisance variables to ensure observed effects are due to the manipulation of the independent variable.

What is a completely randomized design?

An experimental design where each participant is randomly assigned to one treatment condition.

What is a randomized block design?

A design that divides participants into homogeneous blocks based on a relevant characteristic before randomly assigning treatments.

What is a within-subjects (repeated measures) design?

A design where each participant experiences all treatment conditions, often in a random order.

What is the difference between a population and a sample?

A population is the entire group you want to draw conclusions about, while a sample is a subset of the population that you actually measure.

What is normal distribution?

A symmetrical, bell-shaped distribution that describes many natural phenomena, with the mean at the center.

What is the null hypothesis?

A statement of no effect or no difference, typically the hypothesis we are trying to reject.

What is the alternative hypothesis?

A statement of an effect or difference that we suspect to be true, typically what we aim to support.

What does it mean to reject the null hypothesis?

It implies acceptance of the alternative hypothesis, suggesting that the observed results are statistically significant.

What is a Type I error?

Rejecting the null hypothesis when it is actually true (false positive).

What is a Type II error?

Failing to reject the null hypothesis when it is actually false (false negative).

What is the significance level (α)?

The maximum probability of making a Type I error that we are willing to accept, typically set at 0.05.

What is the p-value?

The probability of obtaining a test statistic as extreme as, or more extreme than, the one calculated from the data, assuming the null hypothesis is true.

How are α and p-value related in hypothesis testing?

α is a pre-set threshold for decision-making, while the p-value is calculated from data; if p-value < α, we reject the null hypothesis.

What is the relationship between α and β (Type II error)?

Decreasing α increases β, and vice versa; they are inversely related.

What is the purpose of formulating a statistical hypothesis?

To provide a precise, testable statement about the parameters of one or more populations that can be evaluated using statistical methods.

What does randomization in experimental design help to achieve?

It reduces bias by using chance to assign participants to conditions or determine the order of treatments.

What are quantitative variables?

Variables that measure amounts or degrees, such as drug dosage or test difficulty.

What are qualitative variables?

Variables that represent variations in kind or type, such as teaching strategies or types of psychotherapy.

What are classification variables?

Variables that represent inherent characteristics of subjects, such as age, sex, or species.

What is the role of the F-distribution in hypothesis testing?

It is used to compare observed group differences to assess the role of chance in the context of the null hypothesis.