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Chapter 2

PSYA01H3 Chapter Notes - Chapter 2: Empiricism, Internal Validity, Descriptive Statistics

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Steve Joordens

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Dogmatists thought that the best way to understand illness was to develop theories abou the
human body
Empiricists- thought that the best way to understand sickness was to observe sick people
Dogmatism: the tendency for people to cling to their assumptions
Empiricism: describe the belief that accurate knowledge can be acquired through
Empiricism is the essential element of the scientific method, which is a set of
principles about the appropriate relationship between ideas and evidence.
Theory- a hypothetical explanation of a natural phenomenon.
When scientists set out to develop a theory they start with the simplest one, and
they refer to this as the rule of parsimony, which is credited to William Ockham
Hypothesis: which is a falsifiable prediction made by a theory
Religion - Because such theories do not give rise to hypotheses, they cannot be the
subject of scientific investigation
Edward Muybridge invented a technique where you can take consecutive rapid photos and
proved that all four feet of the horse leave the ground when it gallops.
Empirical method: which is a set of rules and techniques for observation?
3 Things that make People Difficult to Study:
- Complexity
- Reactivity
Psychologists have developed 2 kinds of methods to meet these challenges:
methods of observation, which allow them to determine what people do,
and methods of explanation, which allow them to determine why people do it.
Psychologists cannot simply use casual observations because: they are unstable
and they can’t tell us about all the properties we may be interested in.
Luckily psychologists have developed techniques to work around these:
Measurements & Descriptions.
When measuring you must always do two things: define the property we wish to
measure and then find a way to detect it.
operational definition: which is a description of a property in concrete, measurable
measure: which is a device that can detect the condition to which an operational
definition refers.
electromyograph (EMG) which is a device that measures muscle contractions
under the surface of a person’s skin
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**Having an operational definition that specifies a measurable event and a
device that measures that event are the two keys to scientific
good measures have three properties: validity, reliability and power.
- Validity refers to the extent to which a measurement and a property are
conceptually related.
- Reliability: the tendency for a measure to produce the same measurement
whenever it is used to measure the same thing
- Power: the ability of a measure to detect the concrete conditions specified in the
operational definition.
Demand characteristics are those aspects of an observational setting that cause
people to behave as they think they should
Naturalistic observation is a technique for gathering information by unobtrusively
observing people in their natural environments
- unfortunately many things psychologist want to observe don’t occur naturally,
therefore they have made ways to avoid demand characteristics such as:
Measure behaviours that are not susceptible to demand (pupil dilation)
When people are unaware that a demand and behaviour are related (eye blinking
& concentration)
Keep the people who are being observed “blind”
Use cover stories (filler items)
Observer Bias expectations can influence observations & reality. (rat-maze experiment)
Because both the observer and participant can influence the results, psychological
experiments usually use the method of double-blind observation: which is an
observation whose true purpose is hidden from both the observer and the person
being observed
The most common kind of graphic measurement in psychology is frequency
distribution: which is a graphic representation of measurements arranged by the
number of times each measurement was made
a common shape is the bell curve, which is technically known as the Gaussian
distribution or the normal distribution: which is a mathematically defined
frequency distribution in which most measurements are concentrated around the
-in normal distribution the mean, median and mode are equal
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