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University of Toronto Scarborough
Steve Joordens

PSYA01 K.X C HAPTER 2:M ETHODS IN PSYCHOLOGY Empiricism: How to Know Stuff  2 kinds of doctors long ago: 1. Dogmatists – best way to understand illness was to develop theories about the body’s function 2. Empiricists - best way to understand illness was to observe sick ppl  Empiricism = The belief that accurate knowledge can be acquired through observation The Scientific Method  Empiricism is the essential element of the scientific method  Scientific Method = A set of principles about the appropriate relationship b/w ideas and evidence  Is the Idea = Theory = A hypothetical explanation of a natural phenomenon o The Rule of Parsimony = When scientists start to develop a theory they start with the simplest one (William Ockham)  Hypothesis = A falsifiable prediction made by a theory The Art of Looking  Empirical Method = A set of rules and techniques for observation  Methods = refers primarily to technologies that enhance the powers of the senses  3 Things that make ppl hard to study: 1. Complexity – human brain is complicated 2. Variability – no 2 individuals ever say, think, or do the same thing under the same situations 3. Reactivity – ppl act differently when they are being observed Observation: Discovering What People Do Measurement Defining and Detecting  Operational Definition = A description of a property in concrete, measurable terms  Measure = A device that can detect the condition to which an operational definition refers  Steps to measure a psychological property: 1. Start by developing an operational definition of a property (i.e. use frequency of smiles to determine a person’s happiness) 2. A device that measures these events (i.e. EMG to detect smiles) a. Electromyography (EMG) = A device that measures muscle contractions under the surface of a person’s skin 1 PSYA01 K.X Validity, Reliability, and Power  Good measures have 3 properties: o Validity = The extent to which a measurement and a property are conceptually related o Reliability = The tendency for a measure to produce the same measurement whenever it is used to measure the same thing o Power – The ability of a measure to detect the concrete conditions specified in the operational definition Demand Characteristics  Demand Characteristics – Those aspects of an observational setting that cause ppl to behave as they think they should o Demand/require ppl to say/do things they normally might not say (ex. Do these jeans make me look fat? – no, ofc not.) o To avoid the demand characteristic problem ppl observe others w/o their knowledge  Naturalistic Observation – A technique for gathering scientific info by unobtrusively observing ppl in their natural environments  2 Problems w/ Naturalistic Observation:  Things psychologists want to observe simply doesn’t occur naturally  Some things can only be gathered from direct interaction o Ways to Avoid Demand Characteristics:  Anonymously or privately volunteer info  Behaviours that are not susceptible to demand  Ppl don’t know what the demand and behaviour are related  Blind to the true purpose of the observation – cover stories or filler items Observer Bias o Expectations can influence observations o Expectations can influence reality o Psychologists use many techniques to avoid these influences, such as double-blind observation o Double-blind = An observation whose true purpose is hidden from both the observer and the person being observed Descriptions Graphic Representations  Psychologists often create graphic representations of the measurements they collect: o Frequency Distribution = A graphical representation of measurements arranged by the number of times each measurement was made  Frequency distribution can have any shape but is a common bell shape, which is known as the Gaussian Distribution or normal distribution 2 PSYA01 K.X  Normal Distribution = A mathematically defined frequency distribution in which most measurements are concentrated around the middle  Is symmetrical, peak in the middle, trails off at both ends  Mean, median, and mode are the same unless the distribution is not normal but is positively skewed Descriptive Statistics  Descriptive Statistics = brief summary statement that capture the essential information from a frequency distribution  2 Important Kinds of Descriptive Statistics: o Central Tendency of a frequency distribution = statements about the value of the measurements that tend to lie near the center or midpoint of the frequency distribution  Mode = The value of the most frequently observed measurement  Mean = The average value of all the measurements  Median = The value that is “in the middle” – i.e., greater than or equal to half the measurements and less than or equal to half the measurements  Positively Skewed o Mode and median are lower than the mean o Mean is dragged off toward the tail o Mode stays o Median is b/w the mode and mean o Variability of a frequency distribution  Range = The value of the largest measurement in a frequency distribution minus the value of the smallest measurement  Small range – measurements don’t vary as much  Like the mean it is dramatically affected by an outlier  Standard Deviation = A statistic that describes the average difference between the measurements in a frequency distribution and the mean of that distribution Explanation: Discovering Why People Do What They Do Correlation Patterns of Variation  We can learn about the relationship b/w objects and events by comparing the patterns of variation in a series of measurements  3 Things were done when you performed an imaginary study of insults and requests: o Measured a pair of variables 
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