stats10

# stats10 - Data are produced from ppl machines comp sensors...

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Data are produced from ppl, machines, comp, sensors Data sets consist of sometimes very long strings of numbers We summarize in different ways to understand Course themes How can we compare groups, or see structure How can we determine whether making a change to one factor will result in a change to another How can we determine if differences or changes are due to chance. VARIABLES Numerical: the values of the variable are numbers. For example, weights, counts, prices Categorical: the values of the variable are categories or classifications. For example colors, gender, location. The mode is not reliable for numerical variables Its location varies depending on the width of the histogram bins For large data sets, there can be many modes, or no modes. Put a number on it For symmetric distrubtuions, the sample mean and sample sd measure center and spread For skeweed, use iqr Mean and sd The sample mean, sits at the balancing point of the distribution, it is one measure of center The sd, s, measures the typical distance an observation lies from the sample mean. It is one measure of spread. Median can be another definition of center, bc sometimes mean doesn’t work well with outlires. Medicn is the value that cuts the dist in half. The iqr is the distance spanned by the middle 50% of the data. Sd measures spread or variability in a distribution Like the mesn, sd works best if the distr is symmetric or unimodal

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