Observation and experiment

Observation is the simplest method, but scientific observation differs from everyday noticing. It involves:

• Selection: you cannot watch everything, so you choose the behaviour that matters for your study (a counsellor focuses on what the client says about the problem, not on every gesture).
• Recording: notes, photographs, audio or video, so nothing is forgotten.
• Analysis: going back to the records to find meaning. Good observation is a skill learned over time.

Types of observation:

• Naturalistic: watching behaviour where it normally happens, such as a playground. Controlled: watching it in a laboratory where the researcher can set the conditions.
• Non-participant: the observer stays apart, such as watching a classroom through a camera. Participant: the observer joins the group's activity.
• In participant observation people who know they are being watched may change their behaviour (a teacher who becomes very gentle when the principal walks in). Observers can also bring their own bias.

The experimental method tests cause and effect: does changing one thing change another? Fire causes smoke; does practice cause better recall?

A variable is anything that can vary, that is, take different values: time spent practising, mood, noise level, test score. An object itself (a pen) is not a variable, but its qualities (colour, type of ink) can be.

• Independent variable (IV): the one the researcher changes (manipulates).
• Dependent variable (DV): the one measured to see the effect.
• Extraneous variables: anything else that could affect the DV and spoil the study, such as some participants being unwell. Example: to test whether 20 minutes of daily practice improves typing speed, practice time is the IV, typing speed is the DV, and tiredness or prior experience are extraneous.

Participants are split into an experimental group, which receives the IV (the new practice routine), and a control group, treated the same in every other way but without it, for comparison. Ideally they are placed in groups by random assignment.

Extraneous variables are of three kinds: organismic (the person's own health, anxiety, intelligence), situational/environmental (noise, light, temperature) and sequence (fatigue or practice from doing tasks in a fixed order). They are controlled by:

• Elimination (remove them, e.g. test in a quiet room) and constancy of conditions (keep them the same for everyone).
• Matching (pair people of similar age or ability across groups) and counterbalancing (change the order of tasks between participants).
• Random assignment (spread differences evenly by chance).

• Field experiments are done in real settings (a school) and are more realistic but less controlled.
• Quasi-experiments are used when the IV cannot be manipulated and must be selected instead, such as comparing children who lived through a flood with children who did not. There is no random assignment, because nobody can be assigned to a disaster.