Chpt 13: Understanding Research Results: Statistical Inference (PSY302) Flashcards
Researchers rarely, if ever, study entire ___________; their findings are based on sample data.
populations
Def: Inferential stats
are used to determine whether the results match what would happen if the experiments were repeatedly conducted with multiple samples.
They can also help answer whether it can be inferred that the diff in the sample means reflects a true diff in the population means
Equivalence of groups is achieved by experimentally _________ all other variables or by randomization. The assumption is that if the groups are ________, any diffs in the DV must be due to the effect of the IV.
controlling, equivalent
The diff between any 2 groups will always never be _____.
zero
Inferential stats allow researchers to make ___________ abt the true diff in population on the basis of the sample data.
They give the __________ that the diff between means reflects random error rather than a real diff.
inferences, probability
Def: Null hypothesis
that the population means are equal and that the observed diff is due to random error. That the IV has no effect, this is always going to be the counter/opposite to the research hypothesis.
Def: The research hypothesis
the population means are no equal; that the IV had an effect.
Def: Statistical significance
when there is a low probability that the diff between the obtained sample means was due to random error.
Def: Probability
the likelihood of the occurrence of some event or outcome.
You want to specify the probability that an event will happen if there’s no diff in the population
Def: Sampling distributions
are based on the assumption that the null is true.
Def: Sample size
the total number of observations, which has an impact on determinations of stat significance. Greater size= more confidence.
To use a statistical test, you gotta:
State the null
State the research hypothesis
Find the df and alpha level
Compute the means
Compute the SD and variance
Compute z-scores and t-scores
Compute the amount of error.
Do the Spearman or Pearson r
Def: T test
to examine whether or not the 2 groups are significantly diff or not.
The t uses 2 types of data:
The mean of both the sample and population
The sampling error
Def: Degrees of freedom (df)
represents the number of scores free to vary once the means are known.
Somewhat diff critical values of t are used depending on whether the test is ___________ or has __________.
one tailed, 2 tails
Def: Single tailed tests
research hypothesis specifies the direction of diff right off the bat here.
Def: 2 tailed tests
we don’t know which direction we’re going in our data.
Def: Analysis of variance/F test
more general statistical procedure than the t test.
When a study has only a single IV with 2 groups, F and t are identical.
Analysis of variance is also used when there are more than 2 levels of an IV and when a factorial design with 2 or more IV has been used
The F stat is a ratio of 2 types of variance:
Systematic variance
Error variance
Def: Systematic variance
The deviation of the group means front eh grand mean for mean score of everyone in the population/all groups.
Def: Error variance
the deviation of the individual scores in each group form their respective group means.
The ________ the F ratio is, the more likely it is that the results are _________.
larger, significant
