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25 Cards in this Set
- Front
- Back
Descriptive Statistics Organize Data for?
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-Show the general shape of the data
- Show where the values tend to concentrate -Expose extreme or unusual data values |
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Simple Random Sampling
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-a sample selected so that each item or person in the population has the same chance of being included
-most widely used type of sampling -Ex. Place names in a box - use a table of random numbers |
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Systematic Random Sampling
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a random starting point is selected and then every kth member of the population is selected
-Used to sample from lists Ex: Pulling from a hat -Does not always satisfy definition of random sampling |
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Stratified Random Sampling
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a population is divided into subgroups, called starta and a sample is randomly selected from each stratum
-Used when population can be clearly divided into groups -Reflect the characteristics of a the population than a simple random sample |
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Cluster Sampling
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-a population is divided into clusters using naturally occuring geographic or other boundaries. Clusters are then randomly selected and a sample is collected by randomly selecting from each cluster
-Used to reduce the cost of sampling when the population is scattered over a large geographic area Ex: Different types of advertisers |
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Frequency Table
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a grouping of qualitative data into mutually exclusive classes showing the number of observations in a class
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Equivalence Class
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a single value, a collection of values, or a qualitative category that is used to organize data into a logical fashion
-Some classes may contain no values |
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Class Frequency
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Number of observations in each class
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Relative Frequency
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Fraction of the total number of observations in each class
-the sum of the relative frequencies is always 100 percent |
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Bar Chart
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a. The height of each bar represents the frequency of a certain class
b. The horizontal axis is called the x-axis or abscissa c. The vertical axis is called the y-axis or ordinate d. The point at which the vertical axis and horizontal axis intercept is the origin e. A space exists between the bars |
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Ungrouped frequency table
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A frequency table where each of the class intervals is a single value
-Used for quantitative data |
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Histogram
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-A graph of quantitative data in which the classes are marked on the horizontal axis and the class frequencies are marked on the vertical axis
- The class frequencies are represented by the heights of the bars - The bars are drawn adjacent to each other - Quantitative data can be continuous - Adjacent bars show continuous nature of data - Similar to a bar graph but used for quantitative data rather than qualitative data |
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Difference between a Histogram and a Bar Chart
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Histogram:
-Used with quantitative data -Bars touch Bar graph: - Used with qualitative data -Bars do not touch |
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Mesokurtic
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-Normal Distribution
-Bell Shaped Curve -Symmetric |
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Phtykertic
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-Flatter than normal distribution
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Lyptokurtic
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Skinner than normal distribution
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Negatively Skewed
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Mean < Medain
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Positively Skewed
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Median < Mean
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Bimodal
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Two Bumps
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Multimodal
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Three or more bumps
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J- Shaped
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increasing frequency at an increasing rate(no Hump)
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U Shaped
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increasing then decreasing frequency
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Rectangular
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each class interval has the same frequency
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Frequency Polygon
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- A graph of quantitative data in which line segments connect the points formed by the intersection of the class midpoints and relative class frequencies
- Error in book: Frequency polygons uses frequencies - Frequency polygons are most commonly used with relative frequencies |
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Cumulative Frequency Polygon
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- A graph of quantitative data in which the classes are marked on the horizontal axis and the cumulative relative frequencies are marked on the vertical axis
- If the cumulative frequency polygon is continuous than it is called an ogive |