PSYC218
6/1/26
Descriptive stats
- Describe and summarize characteristics of dataset
- Measures of central tendency (mean, median, mode)- characteristics of
sample
- Measures of variability (range, SD)
- Communicating data through pictures, graphs and tables EG shape of
distribution
Inferential stats
- Using data gathered on a sample to make inferences (draw
conclusions, generalize) about a population
o EG students t-test (we are XX% confident that the interval XX-XX
contains the mean of the population), analysis of variance
- Provides tool for formally testing how likely it is an effect observed is
due to chance or is actually a meaningful pattern
- Patterns in small samples are more likely to be due to chance than
patterns observed in large samples
- Small differences between groups (51% vs 50%) are more likely to be
due to chance than large differences (50% vs 60%)
Statistic: number calculated on sample data that quantifies a characteristic
of the sample EG average value of a sample set
Parameter: number calculated on population data that quantifies
characteristics of population of interest EG average value of a population set
of scores
- You can only estimate the parameter, you can’t know the true value
Revision from Textbook
Methods of knowing
, - Authority
- Rationalism; rules of logic
- Intuition
Vocab
- Population: complete set of interest
- Sample: subset of population
- Variable: any characteristic that may have different values at different
times depending on conditions
- IV: manipulated variable
- DV: measured variable
- Data: measurements made on the subjects
- True experiment: determining whether changes in 1 variable causes
change in another. IV is manipulated and its effect on some DV is
studied
Observational studies
- Naturalistic observation
- Parameter estimation: conducted on samples to estimate the level of 1
or more population characteristics
- Correlational studies
, 8/1/26: Chapter 2
Statistics are denoted with English letters (X, s)
- X or Y typically stands for a variable you have measured
o Xi is the ith score, where i can be a number between 1 and N
- N stands for total number of scores / sample size
Parameters are denoted with Greek letters (μ (mu, mean), σ (sigma, sd))
- Summation = adding things up = Σ (Sigma)
o The sum of the variable X from i =1 to i = N -> ΣX
o Numbers above and below upper sigma indicate the range to be
summed
o BODMAS !
, Measurement scales
- Nominal: qualitative & categorical
o Property of equivalence: all members of a given class are the
same from the standpoint of the classification variable
- Ordinal: quantitative; ranked orders
- Interval: quantitative; ranked orders with equal intervals between
adjacent units
o Scales in psychology which have 5> points such as Likert scale /
anxiety are treated as interval scales under the assumption
intervals between scales are approximately equal in size
o Data should suggest that respondents should interpret questions
as intended, no ‘lumpy’ data
- Ratio: quantitative; equal intervals between adjacent units with an
absolute zero point
Discrete: no possible values between units
- EG number of children, coin flips, touchdowns
Continuous: theoretically has infinite possible values in between units
- EG height, amount of time
- All measures are approximate. Real limits: values that are above and
below the recorded value by ½ of the smallest measuring unit of the
scale
6/1/26
Descriptive stats
- Describe and summarize characteristics of dataset
- Measures of central tendency (mean, median, mode)- characteristics of
sample
- Measures of variability (range, SD)
- Communicating data through pictures, graphs and tables EG shape of
distribution
Inferential stats
- Using data gathered on a sample to make inferences (draw
conclusions, generalize) about a population
o EG students t-test (we are XX% confident that the interval XX-XX
contains the mean of the population), analysis of variance
- Provides tool for formally testing how likely it is an effect observed is
due to chance or is actually a meaningful pattern
- Patterns in small samples are more likely to be due to chance than
patterns observed in large samples
- Small differences between groups (51% vs 50%) are more likely to be
due to chance than large differences (50% vs 60%)
Statistic: number calculated on sample data that quantifies a characteristic
of the sample EG average value of a sample set
Parameter: number calculated on population data that quantifies
characteristics of population of interest EG average value of a population set
of scores
- You can only estimate the parameter, you can’t know the true value
Revision from Textbook
Methods of knowing
, - Authority
- Rationalism; rules of logic
- Intuition
Vocab
- Population: complete set of interest
- Sample: subset of population
- Variable: any characteristic that may have different values at different
times depending on conditions
- IV: manipulated variable
- DV: measured variable
- Data: measurements made on the subjects
- True experiment: determining whether changes in 1 variable causes
change in another. IV is manipulated and its effect on some DV is
studied
Observational studies
- Naturalistic observation
- Parameter estimation: conducted on samples to estimate the level of 1
or more population characteristics
- Correlational studies
, 8/1/26: Chapter 2
Statistics are denoted with English letters (X, s)
- X or Y typically stands for a variable you have measured
o Xi is the ith score, where i can be a number between 1 and N
- N stands for total number of scores / sample size
Parameters are denoted with Greek letters (μ (mu, mean), σ (sigma, sd))
- Summation = adding things up = Σ (Sigma)
o The sum of the variable X from i =1 to i = N -> ΣX
o Numbers above and below upper sigma indicate the range to be
summed
o BODMAS !
, Measurement scales
- Nominal: qualitative & categorical
o Property of equivalence: all members of a given class are the
same from the standpoint of the classification variable
- Ordinal: quantitative; ranked orders
- Interval: quantitative; ranked orders with equal intervals between
adjacent units
o Scales in psychology which have 5> points such as Likert scale /
anxiety are treated as interval scales under the assumption
intervals between scales are approximately equal in size
o Data should suggest that respondents should interpret questions
as intended, no ‘lumpy’ data
- Ratio: quantitative; equal intervals between adjacent units with an
absolute zero point
Discrete: no possible values between units
- EG number of children, coin flips, touchdowns
Continuous: theoretically has infinite possible values in between units
- EG height, amount of time
- All measures are approximate. Real limits: values that are above and
below the recorded value by ½ of the smallest measuring unit of the
scale
