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40 Cards in this Set
- Front
- Back
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Individuals
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the objects described by a set of data. Individuals may be people, but they may also be animals or things.
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Variables
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Any characteristic of an individual. A variable can take different values for different individuals.
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Observational Study
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Any characteristic of an individual. A variable can take different values for different individuals.
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Response
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A variable that measures an outcome or result of a study. The purpose of an observational study is to describe some group or situation
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Levels of Measurement
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-dichotomies
-categorical: nominal and ordinal -continuous: Interval and ratio |
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What are quantitative research methods?
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Statistics and the practice of statistics, and the active practice of statistics through data analysis
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Why are quantitative tools needed?
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-To deal with problems of scale
-to cope with variability by imposing standards -to cope with complexity -to cope with positional effects -to get beyond the taken for granted -to enable thinking in terms of degree. |
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What do quantitative methods offer?
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comparative analysis, rational thinking, meaning in context, a way for determining cause and consequence.
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Three kinds of sociology according to Andrew Abbott
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1) standards causal analysis
2) Social Networks 3) Temporal analysis |
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Experiments
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Deliberately imposes some treatment in individuals in order to observe their responses. The purpose of an experiment is to study whether the treatment causes a change in the response.
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Measure
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A property of a person or thing when we assign a number to represent the property. The result is a numerical variable.
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Valid Measurement
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A variable is a valid measure of a property if it is relevant or appropriate as a representation of that property
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Predictive Validity
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A measurement of a property has predictive validity if it can be used to predict success on tasks that are related to the property measured.
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Errors in measurement:
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measured value= true value+bias+random error
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Bias
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systematically overstates or understates the true value of the property it measures.
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Random error
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Repeated measurements on the same individual give different results.
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Reliable
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Term to describe a random error that is small.
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What is the purpose of using averages?
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To improve reliability. The average of several repeated measurements of the same individual is more reliable than a single measurement
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nominal variables
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Variables with no inherent order or ranking sequence, e.g. numbers used as names (group 1, group 2...), gender, etc.
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Ordinal variables
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Variables with an ordered series, e.g. "greatly dislike, moderately dislike, indifferent, moderately like, greatly like". Numbers (or letters) assigned to such variables indicate rank order only - the "distance" between the numbers has no meaning.Ordinal variables do not establish the numeric difference between data points. They indicate only that one data point is ranked higher or lower than another
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Interval variables
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An interval variable is similar to an ordinal variable, except that the intervals between the values of the interval variable are equally spaced. Interval variables DO NOT have a true zero, e.g. 88 degrees is not necessarily double the temperature of 44 degrees
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Ratio Variables
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as all the properties of an interval variable, but also has a clear definition of 0.0. When the variable equals 0.0, there is none of that variable. Variables like height, age, weight, enzyme activity are ratio variables.
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Median
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The midpoint of distribution, the numbers such that half the observations are smaller and the other half are larger.
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Graphical representation of categorical data
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Pie charts, bar charts, and teh area principle.
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Graphical Representations of quantitative data
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-Stem and leaf
- Histograms -Boxplots -dotplots -Normal Probability plots |
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Tufte Lie Scale
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displayed/ actual
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Quartiles
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Divide observations into quarters
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Quartile 1 (Q1)
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25%, it is the median of the observations whose positions in the ordered list is to the left of the location of the overall median.
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Quartile 2 (Q2)
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75%, it is the median of the observations whose position in the ordered list is to the right of the location of the overall median
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The Five number Summary
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the five-number summary is Minimum→ Q1→ Median →Q3 →Maximum
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Box plots
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is a graph of the five-number summary.
-The central box spans the quartiles. -A line in the box marks the median -Lines extend from the box out to the smallest and largest observations. |
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Why are box plots used?
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for side-by-side comparisons of more than one distribution
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Difference between mean and standard deviation
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Mean measure center, Standard Deviation measures spread.
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Mean x-bar
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It is the clear average of a set of observations.
(sum of the observations)/ n |
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Measures of center
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Mode, Median, Mean, Midrange
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Midrange
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Half the distance between the top and the bottom.
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Measure of spread
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-Range
-Interquartile range -Variation→ variance→ stadard deviation |
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What is standard deviation
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a measure of diversity; the square root of the mean of the squared deviations.
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Building a stadard deviaton
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-Variation: The sum of the squared deviation
-Variance: the mean of the squared deviations -Standard deviaton: the square root of the mean of the squared deviations. -The sum of the deviations is always zero |
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Interquartile Range (IQR)
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The distance between the quartiles
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