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Summary Definitions for Psychology 253
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- Psychology 253
- Institution
- Stellenbosch University (SUN)
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DefinitionsPlease note: it is important to go through the lecture podcasts as these notes do not
serve as an alternative to them. Please don’t send my notes to anyone because I worked
really hard to make these as in depth and easy to understand as possible :)
Chapter 1: Introduction to Statistics
• The term statistics refers to a set of mathematical procedures for organising, summarising and
interpreting information
• A population is the set of all the individuals of interest in a particular study
• A set of individuals selected from a population and intended to represent the population is called a
sample.
• A variable is a characteristic or condition that changes or has different values for different individuals
• The measurement obtained for each individual is called a datum (or score or raw score). This is a single
measurement or observation which is commonly called a score or raw score
• The complete set of scores is called the data set or simple the data. Data is the measurements or
observations. A data set is the collection of measurements or observations
• A parameter is a value (usually a numerical value) that describes a population and is derived from
measurements of the individuals in a population
• A statistic is a value (usually a numerical value) that describes a sample and is derived from
measurements of the individuals in the sample
• Descriptive statistics are statistical procedures that are used to summarise, organise and simplify data
• Inferential statistics consist of techniques that allow us to study samples and then make generalisations
about the populations from which they were selected
• A sampling error is the natural occurring discrepancy or error that exists between a sample statistic and
the corresponding population parameter
• Constructs are internal attributes or characteristics that cannot be directly observed but are useful for
describing and explaining behaviour
• An operational definition identifies a measurement procedure ( a set of operations) for measuring an
external behaviour and uses resulting measurements as a definition and a measurement for a
hypothetical construct. It has 2 components namely; describes a set of operations for measuring a
construct and defines the construct in terms of the resulting measurements
• A discrete variable consists of separate, indivisible categories and there are no intermediate values
between adjacent categories.
• Continuous variable contain an infinite number of possible values that fall between any two observed
values and is divisible into an infinite number of fractional parts
• Real limits are the boundaries of intervals for scores that are represented on a continuous number line.
The real limit separating two adjacent scores is located exactly halfway between the scores. Each score
has two real limits.
• The upper real limit is at the op of the interval and the lower real limit is at the bottom
• Nominal Scales consist of a set of categories that have different names. Measurements on a Nominal
scale label and categorise observations but do not make any quantitative distinctions between
observations
• An ordinal scale consists of a set of categories that are
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Notes by: Michaela Goncalves
22587934
, organised in an ordered sequence and measurements rank observations in terms of size or magnitude
• The value of zero is assigned to a particular location on the scale simply as a matter of convenience or
reference
• An interval scale consists of ordered categories that are all intervals exactly the same size. Equal
differences between numbers on scale reflect equal differences in magnitude. However, the zero point on
an interval scale is arbitrary and does not indicate a zero amount of the variable being measured
• A ratio scale is an interval scale with the additional feature that a score of zero indicates non of the
variable being measured. With a ratio scale, ratios of numbers do reflect ratios of magnitude
• Descriptive research or descriptive research strategy involves measuring one or more separate variables
for each individual with the intent of simply describing the individual variables
• When a study allows more than one explanation for the results, the study is said to be confounded
because it is impossible to reach an unambiguous conclusion
• In the experimental method, one variable is manipulated while the other variable is observed and
measured. To establish a cause and effect relationship between two variables, an experiment attempts to
control all other variables to prevent them from influencing the results
• The independent variable is the variable that is manipulated by the researcher. In behavioural research,
the independent variable usually consists of the two or more treatment conditions to which subjects are
exposed. The independent variable is manipulated prior to observing the dependent variable
• Individuals in a control condition do not receive the experimental treatment. Instead they either receive no
treatment or they receive a neutral, placebo treatment. The purpose of a control condition is to provide a
baseline for comparison with the experimental condition
• Individuals in the experimental condition do receive the experimental treatment
Chapter 2: Frequency Distributions
• A frequency distribution is an organised tabulation showing the number of individuals located in each
category on the scale of measurement
• Proportion describes the distribution of scores which can be incorporated into the table
• These express the relative frequency out of 100
• The groups or intervals in a grouped frequency distribution table are called class intervals
• A relative frequency is when you the score you get when you can’t find the absolute frequency and
instead shows a relative frequency
Chapter 3: Central Tendency
• Central tendency is a statistical measure to determine a single score that defines the centre of a
distribution. The goal of central tendency is to find the single score that is most typical or most
representative of the entire group
• If the scores in a distribution are listen in order from smallest to largest, the median is the midpoint of the
list. More specifically, the median is the point on the measurement scale below which 50% of the scores
in the distribution are located
• The mode is the score or category that has the greatest frequency of any score in the frequency
distribution
Notes by: Michaela Goncalves
Chapter 4: Variability 22587934
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