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20 Cards in this Set
- Front
- Back
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kurtosis
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- without changing the mean
- vertical distortion |
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leptokurtosis
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- high middle
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platykurtosis
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- lower middle
- can be flat |
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negative skew
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higher data values predominate
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postivie skew
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lower data values predominate
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statistics
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- values calculated from sample data used to estimate a value or parameter in a larger population
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point estimate
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a single statistic calculated from sample observations used to estimate the numerical value of a particular population parameter
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statistical significance testing
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tells us how much statistical determinations are expected to vary due to chance variations in random sample
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two-tailed test
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- investigator can't be sure that the population's parameter is greater or less than the null hypothesis
- most common |
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one-tailed test
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- used when the direction of the relationship being studed is known and analysis is only concerned with determining the strength of the relationship
- greater statistical power |
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dependent variables
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- the study outcome or endpoint
- usual approach: analyze one such variable at a time |
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independent variable(s)
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- variable(s) measured to estimate the corresponding measurement of the dependent variable
- defines the conditions under which the dependent variable is to be measured |
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univariable analysis
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- 1 dependent variable, no independent variable
- estimation of the probability of a disease without regard to any characteristic such as age, gender, diet |
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bivariable analysis
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- 1 dependent variable, 1 independent variable
- determining the if there is an assciation between birth control pill use and stroke |
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multivariable analysis
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- 1 dependent variable, >1 independent variable
- determining the likelihood of stroke for femails, of different ages and smoking status - also used to adjust for confoudning variables |
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continuous data
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- the range of measurement is any number of equally spaced numerical values between any two points
- measure on ratio or interval scales - a great number of possible values exist - ex. serum cholesterol, age, weight - wide range of values |
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ordinal data
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- discrete data
- the interval between consecutive measurements is not necessarily known or constant - ordered sequence - ex. number of pregancies, scoring systems, mammogram interpretation, cancer staging - limited number of possible variables |
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nominal data
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- data which is not ordered is measured on a nominal scale
- ex. eye color, gender - the number of nominal variables is the number of categories minus one |
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rescaling of data
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- age to age range to young, old description
- shifting down results in the loss of information - statistical power reduced, increasing the likelihood of type II error |
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Uses of univariable analysis
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1.) Descriptive studies - clinical and lab results on a group of diseased patients
2.) Descriptive measurements of the study sample 3.) Comparison, using 2 measurements, with the same or paired individuals: a special situation - a hypothesis may be tested in some cases, no independent variable *ex. a blood pressure determination made twice on the same individual, or on two paired similar individuals |
