305 - A&A Chapter 1 Numbers Descriptive stats: used to...

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A&A Chapter 1 – Numbers Descriptive stats : used to summarize and make understandable a group of numbers from a research study. des stat summarize, simplify and describe a large number of measurements. Inferential stats : used to draw conclusions and make inferences based on the numbers from a research study, but that go further than the numbers. help researchers interpret what the data means. Numeric variables : the scores are numbers that tell you how much there is of what is being measured. Ex. 1-10 how stressed are you. Equal - interval variables : variables in which the numbers stand for about equal amounts of what is being measured. Ex . GPA Ratio - scale : EI variables are on a ratio scale if it has an absolute zero point. EI variables can also be discrete or continuous. Discrete variables can only have specific values. No intermediate values allowed. Continuous variables can have an infinite number of values. Time, height, weight are an ex. Rank order (ordinal) variables are variables in which the numbers stand only for relative ranking. Categorical (nominal) variables are variables in which the values are names.
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Ex. Religion, gender. Qualitative. A frequency table is a table listing how often a score was used. Also listed is the percent and variable measured. Combined categories (5-7, 8-10) are called intervals . They are used on grouped frequency tables. If distribution has 1 high point , it is called unimodal . 2 ? Bimodal . 3 ? Multimodal . Floor and ceiling effect are when scores on the low/high end pile up because you can't have a lower/higher score. Kurtosis is how much the shape of a distribution differs from a normal curve. 4 properties of the abstract number system--
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identity magnitude equal intervals true zero Identity means that each number has a particular meaning. Magnitude means each number has an inherent order from smaller to larger. EI is when the difference between units is the same anywhere on the scale. True zero indicates that the zero on the scale indicates represents a zero level of the
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This note was uploaded on 04/10/2008 for the course ASTR 121 taught by Professor Tolbert during the Spring '08 term at UVA.

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305 - A&A Chapter 1 Numbers Descriptive stats: used to...

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