Lecture 3 Flashcards
define population
all possible observations about which we would like to know something
- realistically we can’t test the entire population
define sample
a set of observations drawn from the population of interest
- subset of a population
define random sample
is one in which every member of the population has an equal chance of being selected into the study
- not possible to completely randomize
define convenience sample
is one that uses participants who are already available
- lower generalizability
- most common form of sampling
ex. first year psych students
define generalizability/external validity
the researcher’s ability to apply findings from one sample or in one context to other samples or contexts
What does WEIRD sample stand for?
Western Educated, Industrialized, Rich, and Democratic
- not a diverse sample
- may be a bias convenience sample
volunteering
- self selected
- crowdsourcing
- online network sampling
- issues with reliability and validity with some research
online network sampling
- easy to falsify data
How to reduce threats to generalizability
replication - the duplication of scientific results, ideally in a different context or with a sample that has different characteristics
constraints on generality statements (COG) - a statement of the target population to which the study’s results should generalize
define probability
the likelihood that a particular outcome – out of all possible outcomes – will occur
- the proportion that we expect to find (percentage)
- probabilistic reasoning is used by psych and other sciences
- rarely speak in absolutes
- terms like on average, in general, etc.
threats to probability
- anecdotal evidence: relating experience/testimonials
- confirmation bias: our usually unintentional tendency to pay attention to evidence that confirms what we already believe and to ignore evidence that would disconfirm our beliefs
- illusory correlation: the phenomenon of believing one sees an association between variables when no such association exists (no scientific evidence)
define personal probability
a person’s own judgment about the likelihood that an event will occur
- assuming there is a likelihood for an outcome
- not scientific
define expected relative-frequency probability
the likelihood of an event occurring, based on the actual outcome of many, many trials
How to calculate probability
- determine total number of trials
- determine the number of trials with successful outcomes
- divide the number of successful outcomes by the number of trials
define proportion
the number of successes divided by the number of trials (decimal)
define percentage
simply probability or proportion multiplied by 100
Statistical probability requires that the individual trials be _____
independent
define inferential statistics
find a significant relationship between 2 variables in a sample and the data can then be applied to the larger population
define null hypothesis
- H0
- Statement that usually postulates that there is no difference between populations or that the difference is in a direction opposite to that anticipated by the researcher
research/alternative hypothesis
- H1
- Statement that usually postulates that there is a difference in a certain direction between populations
control vs. experimental group
- control receives no treatment (or placebo)
- experimental group gets treatment
what does it mean to reject the null hypothesis
When the data suggest that there is a mean difference, we reject the idea that there is no mean difference.
- Conclude that a difference is found
what does it mean to fail to reject the null hypothesis
We fail to reject the null hypothesis; no mean difference
- Conclude that no difference is found
________ are used to test the null hypothesis
statistics
