choosing the appropriate statistics dr. erin devers october 17, 2012
TRANSCRIPT
Choosing the Appropriate StatisticsDr. Erin DeversOctober 17, 2012
Quantitative or Qualitative? Is the data quantitative or qualitative? If qualitative, you have to do the hard
work of coding the material numerically before analyzing it.
Level of Measurement? Nominal
Descriptive stats: mode Inferential stats: chi-square
Ordinal Descriptive stats: median
Interval/Ratio Descriptive stats: mean and standard
deviation Inferential stats: it depends
Chi-Square (ϰ2) Indicates whether a distribution of
frequencies is what you would expect If distribution is significantly different
from what is expected, then it suggests there is a true difference present
Examples
Example: Are more males or females diagnosed with schizophrenia?
Male Female
50 50
Guys Girls
70 30
* p < .001
Interval/Ratio Data: Did you conduct an experiment? Correlation and Regression t-test, ANOVA
Correlation Joke
Correlation Coefficient:
Definition: number that represents the relationship between two variables.
Answers the question, how are changes in X related to changes in Y?
Gives you information regarding
Strength of the relationship
Direction of the relationship
Linear Regression
Basic premise: given previous observations, one can (within some range of error) predict what is likely to occur in futureExamples: GRE scores and performance in grad school Parental smoking and smoking in teens Cholesterol level and risk for heart attack. Maternal depression and childhood
psychopathology Workers level of responsibility and job
satisfaction Beliefs and what one will do within a certain
situation.
t-tests Provide a way to compare two group
means with each other Paired or Independent (depends on
whether you used a between or within subjects design)
ANOVA: Analysis of Variance F statistic Takes into account the fact that chances
of getting a difference randomly goes up with multiple comparisons.
F = t2
Comparing means of multiple groups
e.g. What dose of a drug works best for arresting hallucinations in schizophrenia?
Questions?