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Basics of Statistics
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Statistics the science of collecting, organizing, analyzing, and drawing conclusions from data
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Descriptive statistics
the methods of organizing & summarizing data
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Inferential statistics
involves making generalizations from a sample to a population
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Population The entire collection of individuals or objects about which information is desired
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Sample A subset of the population, selected for study in some prescribed manner
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Variable any characteristic whose value may change from one individual to another
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Data observations on single variable or simultaneously on two or more variables
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Types of variables
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Categorical variables
or qualitative identifies basic differentiating characteristics of the population
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Numerical variables or quantitative
observations or measurements taken on numerical values makes sense to average these values two types - discrete & continuous
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Discrete (numerical) listable set of values usually counts of items
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Continuous (numerical)
data can take on any values in the domain of the variable usually measurements of something
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Classification by the number of variables
Univariate - data that describes a single characteristic of the population Bivariate - data that describes two characteristics of the population Multivariate - data that describes more than two characteristics (beyond the scope of this course
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Identify the following:
gender age hair color smoker systolic blood pressure number of girls in class categorical numerical
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Types of Distributions
4 common types
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Symmetrical refers to data in which both sides are (more or less) the same when the graph is folded vertically down the middle bell-shaped is a special type has a center mound with two sloping tails
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Uniform refers to data in which every class has equal or approximately equal frequency
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Skewed (left or right) refers to data in which one side (tail) is longer than the other side the direction of skewness is on the side of the longer tail
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Bimodal (multi-modal)
refers to data in which two (or more) classes have the largest frequency & are separated by at least one other class
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Dotplots Stem & leaf plots Histograms Boxplots
How to describe a graph Dotplots Stem & leaf plots Histograms Boxplots Do after Features of Distributions Activity
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1. Center discuss where the middle of the data falls
three types of central tendency mean, median, & mode
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2. Spread discuss how spread out the data is
refers to the variability of the data Range, standard deviation, IQR
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3. Type of distribution refers to the overall shape of the distribution symmetrical, uniform, skewed, or bimodal
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4. Unusual occurrences outliers - value that lies away from the rest of the data gaps clusters anything else unusual
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5. In context You must write your answer in reference to the specifics in the problem, using correct statistical vocabulary and using complete sentences!
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