section 3: data analysis

• What kind of test is used for nominal data and related designs (repeated measures or matched pairs)?


  A sign test
• What kind of test is used for nominal data and independent design?


  Chi squared
• What kind of test is used for ordinal data and related designs (repeated measures or matched pairs)?


  Wilcoxon
• What kind of test is used for ordinal data and independent design?

  Mann-Whitney
• What kind of test is used for ordinal data and a correlation?

  Spearman's Rho
• What kind of test is used for interval data and related designs (repeated measures and matched pairs)?


  Related t-test
• What kind of test is used for interval data and independent design?


  Unrelated t-test
• What kind of test is used for interval data and a correlation?

  Pearson's r
• Histograms are used for continuous data.
• A type 1 error is a false positive. This is where there is believed to be a real difference in the data produced where there is not, so the hypothesis is accepted in error.
• A type 2 error is a false negative. This is where a real difference in data is overlooked and the null hypothesis is accepted in error.
• A 5% level of significance is used in psychological research because it strikes a balance between the risk of making a type 1 and type 2 error.
• Nominal data is categorical. Ordinal and interval data are rated on a scale. Ordinal is subjective. Interval is objective.
• A sign test is done by seeing if the results increase, decrease or stay the same for each pair/individual across the categories. If it stays the same disregard this bit of data from the total. Add up all the increases (+) and all the decreases (-). Whichever is smallest is S.
• Concurrent validity is where there is a close agreement in data between a new test and an old test. There must be a coefficient between the two sets of data of +0.8 or more.
• Scattergraphs are used to display correlations. They indicate the relationship between co-variables.
• In a meta-analysis, combined data is often statistically tested to provide an overall conclusion.
• A symmetrical/normal distribution of data occurs when the mean is equal to the mode/median.
• A positive skew in distribution occurs when the mean is greater than the mode/median.
• A negative skew in distribution occurs when the mean is less than the mode/median.
• A content analysis is a method of quantifying qualitative content via coding/categorisation.
• Standard deviation is a measure of the average amount that scores differ from the mean; it is the average variance. Variance is the amount the results are spread around the Mean.
• Types of graph and what they are used for:

  • Scattergrams - correlations
  • Bar charts - difference between conditions
  • Pie chart - which parts/proportions make up a whole
  • Histograms - frequency/spread of scores in one set of related data e.g. from one condition
• In a histogram the bars should always touch as the data is continous. In a bar chart the bars should have gaps between them if they are from different conditions. If there are different elements in just one condition then these bars can touch and you will need a key to show which is which as only the IV label should go on the X axis.