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NU Research Methods
Statistical Methods Flashcards 1
| Question | Answer |
|---|---|
| range | length of the smallest interval which contains all the data |
| interquartile range (IQR) | difference between the third and first quartiles |
| Variance | amount of variation of all the scores for a variable s(square)=sum (x-mean(x))(square)/N |
| Standard Deviation | square root of variance |
| Normal Distribution | two-thirds of cases within one standard deviation of the mean two-thirds of cases within one standard deviation of the mean approximately 95% of cases within two standard deviations of the mean |
| Deviation | x-x(mean) |
| Experimental research design | a scientific control is used to minimize the unintended influence of other variables Random assignment of subjects |
| Quasi-experimental design | Experimental method but without random assignment |
| When is quasi experimental design used? | when randomization is impossible and/or impractical |
| Advantages of quasi experimental design | Easier minimizes threats to external validity efficient in longitudinal research |
| Disadvantages of quasi experimental design | Threats to internal validity Causal relationships difficult to determine Confounding variables |
| Internal validity | extent to we can accurately state that the independent variable produced the observed effect |
| Threats to internal validity | regression to the mean confounding variables extraneous variable occurring between pre- and post-measurement maturation instrumentation error investigator bias differential attrition |
| External validity | Generalizability – to or across target populations – to or across tasks – to or across environments |
| Threats to external validity | situation or environment Hawthorne effect (testing effect) Rosenthal effect Selection bias pre and post test effects |
| Hawthorne effect | People act differently when they know they are being tested |
| Non-experimental design | No control group Observational Used for theory development |
| cross tabulation | A table of the frequency distribution of two or more variables |
| Null hypothesis | hypothesis of no difference Something happens by chance or that no difference exists between populations |
| Chi-square (χ2) | compares a set of frequencies expected if the null hypothesis is true (fe) against a set of frequencies observed in a sample (fo) |
| Geometric mean | used for data based on ratios, proportionate growth, percentage change. |
| differential attrition | extent of subjects who drop out of a study AKA mortality |
| reliability | consistency of observations not the same as validity (could be consistently false) reliability is necessary BEFORE validity can be established |
| Social desirability effect | Subject respond in a way that appears favorable to the tester |
| Advantages of interviews | higher response rate more lengthy and detailed more complex more flexible linking |
| Advantages of questionnaires | low cost protectivity (confidential) less reactivity |
| reactivity | act of measuring changes responses |
| Cohort study | Compare group of people who share a certain characteristic (smokers) with unexposed group(non-smokers). |
| Experimental trial | Exposed v. unexposed groups in trial setting (drug v. placebo) |
| Case control study | Historical, Subjects already have a condition, study looks back to see if there are characteristics of these patients that differ from those who don’t have the disease |
| Odds Ratio | Probability that something will occur divided by probability it will not occur. |
| Kurtosis | Measure of peakedness in frequency distributions |
| platykurtic | lower, wider peak around the mean |
| leptokurtic | a more acute peak around the mean (bunching toward the mean) |
| skewness | a measure of the asymmetry of the probability distribution |
| positive skew | Tail to the right is longer |
| negative skew | Tail to the left is longer |
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