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cross-sectional data
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Look at different units (or cross-sections) \(i\) at a single point in time
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data set
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A collection of numerical values for individual observations, separated into distinctive variables
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descriptive statistics
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Summarise information about the centre and variability of a variable
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deviation
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The deviation \(d\) of an observation \(y_{i}\) from the sample mean \(\bar{y}\) is the difference between them: \(d=y_{i}-\bar{y}\)
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interquartile range
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The difference between the 3\(^{\text{rd}}\) and the 1\(^{\text{st}}\) quartiles
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mean
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Is equal to the sum of the observations divided by the number of observations
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median
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Separates the lower half from the upper half of observations
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mode
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Is the most frequently occurring value
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percentile
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In ordered data, the percentile refers to the value of a variable below which a certain proportion of observations falls
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primary data
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Primary data are data you have collected yourself
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quartile
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Divides ordered data into four equal parts and indicates the percentage of observations that falls into the respective quartile and below
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range
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The difference between the largest and the smallest observation
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secondary data
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Secondary data are data which have been collected by somebody else
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standard deviation
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The standard deviation s is defined as \[\begin{equation*}s=\sqrt{\frac{\text{sum of squared deviations}}{\text{sample size} -1}}=\sqrt{\frac{\Sigma(y_{i} - \bar{y})^2}{n-1}}\end{equation*}\]
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variance
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Is equal to the squared standard deviation
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