# 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

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