Colin Donnelly-
Measures of central tendency
Measures of central tendency provide a single value representation for the middle of a group of data.
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Arithmetic mean or average
The arithmetic mean or average is a measure of central tendency that equally weighs all values; it is most affected by outliers.
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Median
The median is the value that lies in the middle of the data set. Fifty percent of data points are above and below the median.
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Mode
The mode is the data point that appears most often; there may be multiple (or zero) modes in a data set.
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Distributions can be classified by _____ and _____.
measures of central tendency
measures of distribution
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The normal distribution is _____.
symmetrical
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The _____ are all the same in the normal distribution.
mean, median, and mode
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Standard distribution
The standard distribution is a normal distribution with a mean of zero and a standard deviation of one; it is used for most calculations.
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_____ of data points occur within one standard deviation of the mean, _____ within two, and _____ within three.
68%
95%
99%
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Skewed distributions
Skewed distributions have differences in their mean, median, and mode; the skew direction is the direction of the tail of the distribution.
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Bimodal (multimodal) distributions
Bimodal distributions have multiple peaks, although not necessarily multiple modes, strictly speaking. It may be useful to perform data analysis on the two groups separately.
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Range
Range is the difference between the largest and smallest values in a data set.
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Interquartile range
Interquartile range is the difference between the value of the third quartile and first quartile; interquartile range can be used to determine outliers.
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Standard deviation
Standard deviation is a measurement of variability about the mean; standard deviation can also be used to determine outliers.
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Outliers may be a result of _____, _____, or _____.
true population variability
measurement error
a non normal distribution
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Procedures for handling outliers should be ...
... formulated before the beginning of a study.
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Independent events
The probability of independent events does not change based on the outcomes of other events.
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Dependent event
The probability of a dependent event changes depending on the outcomes of other events.
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Mutually exclusive outcomes
Mutually exclusive outcomes cannot occur simultaneously.
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Exhaustiveness
When a set of outcomes is exhaustive, there are no other possible outcomes.
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Hypothesis tests
Hypothesis tests use a known distribution to determine whether a hypothesis of no difference (the null hypothesis) can be rejected.
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Whether or not a finding is statistically significant is determined by the comparison of a _____ to the selected _____.
p-value
significance level (α)
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Confidence intervals
Confidence intervals are a range of values about a sample mean that are used to estimate the population mean. A wider interval is associated with a higher confidence level (95% is common).
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_____ and _____ are both used to compare categorical data.
Pie charts (circle charts) and bar charts
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_____ and _____ are both used to compare numerical data.
Histograms and box plots (box-and-whisker plots)
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Maps are used to compare ...
... up to two demographic indicators.
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Linear, semilog, and log–log plots can be distinguished by their _____.
axes
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Slope can be calculated most easily from _____.
linear plots
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Correlation and causation are separate concepts that are linked by _____.
Hill’s criteria
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Data must be interpreted in the context of _____ and _____.
the current hypothesis
existing scientific knowledge
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_____ and _____ significance are distinct.
Statistical and practical significance
