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12 Cards in this Set
- Front
- Back
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What is a statistical test used for? |
To determine whether a difference or an association found in a particular investigation is statistically significant and more than could have occurred by chance. |
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What is the outcome of a statistical test? |
Whether we accept or reject the null hypothesis |
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What are the three factors when deciding what statistical test to use? |
1. Whether a researcher is looking for a difference or correlation 2. In the case of a difference, what experimental design is being used 3. The level of measurement |
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Describe the first factor used to decide the correct statistical test: |
Difference or correlation -relates to aim or purpose of the investigation -should be obvious through the wording of the hypothesis -correlation can include correlational analyses as well as invetsigations that are looking for an association. |
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Describe the second factor used to decide the correct statistical test: |
Experimental design -independent groups, repeated measures and matched pairs -repeated measures and matched pairs are related designs; in repeated measures the same people are used for all conditions and in matched pairs participants in different conditions aren't the same but have been matched on a variable that is important for the investigation making them related.= related designs -Each particpant in independent groups design is different meaning the design is unrelated. -Thus the researcher chooses from two alternatives; related or unrelated deisgn. -If the investigation is looking for a correlation rather than a difference then this factor is missed. |
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Describe the third factor used to decide the correct statistical test: |
Levels of measurement -Quantitative data can be divided into different levels of measurement; nominal, ordinal and interval. |
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What is nominal data? |
-Data represented in the form of categories (categorical data). -Discrete= one item can only appear in one of the categories Example= if you ask someone their most liked sweet their vote will only appear in one category. |
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What is ordinal data? |
-Data that is ordered in some way; ratings -Does not have equal intervals between each unit as it would not make sense to say someone who rated something an 8 likes it twice as much as someone who gave it a 4. -Lacks precision as it is based on subjective opinion rather than objective measures; what constitutes a 4 or an 8 for the people rating may be quite different. =unsafe data -Not used as part of statistical testing; raw scores are converted to ranks instead and those are used in the calculation. |
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What is interval data? |
-Contrast to ordinal data -Based on numerical scales that include units of equal, precisely defined size= more detail is preserved -Measurements that produce data based on accepted units of measurement (time, temperature, weight) -Most precise and sophisticated form of data in psychology and is necessary criterion for the use of parametric tests. |
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What are parametric tests? Give examples |
-More powerful and robust than other tests -If a researcher is able to use a parametric test they will as these tests may be able to detect significance within some data sets that non-parametric tests cannot. = related t-test, unrelated t-test, Pearson's r |
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