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Unit 1 - Graphs and Distributions
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Statistics 4 the science of collecting, analyzing, and drawing conclusions from data
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Descriptive statistics 4 the methods of organizing & summarizing data
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Inferential statistics 4 involves making generalizations from a sample to a population
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ASK??? 4 Who? –What individuals…. –How many ….. 4 What? –Variables… –Exact definitions… –Units 4 Why?
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Population 4 The entire collection of individuals or objects about which information is desired
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Sample 4 A subset of the population, selected for study in some prescribed manner
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Variable 4 any characteristic whose value may change from one individual to another
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Data 4 observations on single variable or simultaneously on two or more variables
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Types of variables
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Categorical variables 4 or Qualitative variables 4 identifies basic, differentiating characteristics of the population
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Numerical variables 4 or Quantitative variables 4 observations or measurements take on numerical values 4 makes sense to average these values 4 two types - discrete & continuous
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Problem 1.1 Page 7 4 What are the individuals in this data set? 4 For each individual, what variables are given? Which of these variables are categorical and which are quantitative?
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Discrete (Numerical) 4 listable set of values 4 usually counts of items
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Continuous (Numerical) 4 data can take on any values in the domain of the variable 4 usually measurements of something
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Classification by the number of variables 4 Univariate - data that describes a single characteristic of the population 4 Bivariate - data that describes two characteristics of the population 4 Multivariate - data that describes more than two characteristics (beyond the scope of this course
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Identify the following: 4 gender 4 age 4 hair color 4 smoker 4 systolic blood pressure 4 number of girls in class 4 categorical 4 numerical 4 categorical 4 numerical
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Types of Graphs 4 Bar Graph – pg 9 4 Pie Charts – pg 9 4 Dotplots – pg 11 4 Stem & Leaf – pg 13 4 Histogram – pg 19 4 Time plot – pg 31 4 Box & Whisker – pg Categorical Variables
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Problem 1.8 (a) page 17
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Caffeine Content (mg) per 8-ounce serving of various soft drinks Key: 3|5 means the soft drink contains 35 mg of caffeine per 8-ounce serving.
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Caffeine Content (mg) per 8-ounce serving of various soft drinks Key: 3|5 means the soft drink contains 35 mg of caffeine per 8-ounce serving.
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Types of Distributions 4 common types
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4 Distribution – tells us what values the variable takes and how often it takes the values.
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Symmetrical 4 refers to data in which both sides are (more or less) the same when the graph is folded vertically down the middle 4 bell-shaped is a special type –has a center mound with two sloping tails
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Uniform 4 refers to data in which every class has equal or approximately equal frequency
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Skewed (left or right) 4 refers to data in which one side (tail) is longer than the other side 4 the direction of skewness is on the side of the longer tail
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Bimodal (multi-modal) 4 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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How to describe a graph Dotplots Stem & leaf plots Histograms Boxplots
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1. Center 4 discuss where the middle of the data falls 4 three types of central tendency –mean, median, & mode
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2. Spread 4 discuss how spread out the data is 4 refers to the variability of the data –Range, standard deviation, IQR
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3. Shape of the Distribution 4 refers to the overall type of the distribution 4 symmetrical, uniform, skewed, or bimodal
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4. Unusual occurrences 4 outliers - value that lies away from the rest of the data 4 gaps 4 clusters 4 anything else unusual
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5. In context 4 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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