# Stat Exam 1

## Terms

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- Statistics
- The branch of mathematics that transforms data into useful information for decision makers
- Descriptive Statistics
- collecting, summarizing, and describing data. (how many of something. surveys, tables, graphs and sample mean)
- Inferentail Statistics
- drawing conclusions and or making decisions concerning a population based only on sample data
- Variable
- a characteristic of an item or individual
- Data
- the different values associated with a variable
- Operational definitions
- universally accepted meanings that are clear to all associated with an analysis. Variable values are meaningless without this.
- Population
- consists of all the times or individuals about which you want to draw a conclusion on
- Sample
- the portion of a population selected for analysis
- Parameter
- a numerical measure that describes a characteristic of a population. it is a constant/fixed value
- Statistic
- a numerical measure that describes a characteristic of a sample. varible value, changes from one sample to another
- Primary Sources
- the data collector is the one using the data for analysis. data is collected from a survey or experiment, or observed
- Secondary Sources
- The person performing the data analysis is not the data collector. You can buy or view it in journals.
- Categorical Variables
- have values that can only be placed into categories such as yes and no. I.E. male/female, eye color, marital status
- Numerical bariables
- have values that represent quantities. IE # children (discrete) weight (continuous)
- Nominal scale
- classifies data into distinct catefories in which no ranking is implied
- Ordinal scale
- classifies data into distinct categories in which ranking is implied
- Interval scale
- an ordered scale in which the difference between measurements is a meaningful quantity but the measurements do not have a true zero point
- Ratio scale
- an ordered svale in which the difference between the measurements is a meaningful quantity and the measurements have a true zero point
- Central tendency
- the extent to which all the data values group around a typical or central value
- variation
- the amount of dispersion or scattering of values
- shape
- the pattern of the distribution of values from the lowest value to the highest value
- mean
- most common measure of central tendency. all sum of values divided by the number of values
- median
- the middle number. ranks from smallest to largest. n + 1 divided by two gives you the ranked value
- mode
- value that occurs most often. isn't always one.
- first quartile position
- Q1=(n+1)/4, ranked value
- second quartile position
- Q2= (n+1)/2, ranked value
- third quartile position
- Q3=3(n+1)/4, ranked value
- range
- largest value - smallest value. number of units the data takes up
- interquartile range
- 3rd quartile - 1st quartile. can eliminate some high and low values and calcualte the range from the remaining values
- variance
- the average of the square deviations of values from the mean. every value minus the mean, square each, add up and divide by the sample size minus 1.
- Standard deviation
- compute difference btwn value and mean. square each difference. add squared differences together. divide by n - 1, get sample variance. sqaure root of that to get standard deviation
- Z-score
- Z= X-M / SD
- left skewed
- mean < median
- right skewed
- median < mean
- symmetric
- mean = median
- population mean
- sum of the values in the population divided by the population size