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STAT 2220 Exam 2
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Gravity
Terms in this set (49)
Probability Of an Event
the proportion of times the event is expected to occur when the experiment is repeated under identical conditions
3 General methods to find probability
Theoretical
Empirical
Personal
Theoretical
based on theory
Example of Theoretical
Flipping coins; the coin is fair and both sides are equally likely to occur
Empirical
based on data
Example of Empirical
Testing cell phones
Personal
based on individuals judgement
Example of Personal
Clemson Sports; CU wins next game
Sample Space
a list of all outcomes
What is one method used to create a sample space (ss)
Tree Diagram
Independent
define probabilities without regard to previous branches/units
Example of Independent
No matter if you flip a head or a tail it's always a 50% (.5) chance; the second is not affected by the first
Expected Value
Multiplying each outcome by it's probability and then summing over all possible outcomes will tell you the ..
Combination
The number of ways to choose "r" objects from a set of "n" objects without replacement and without regard to order
Random Variable
assumes numerical values associated with random outcomes of an experiment, where one (and only one) numerical value is assigned to each outcome
Two types of Random Variables
Discrete RV
Continuous RV
Discrete RV
assumes a countable number of distinct possible values
Continuous RV
assumes an infinitely large number of values corresponding to points on a line interval
Number of cars in parking lot at certain time at night, or number of people attended the boston college game at certain time
Example of Discrete RV
The amount of time someone runs a race, weight, height, time
Example of Continuous RV
Binomial RV
a series of trials with two outcomes for each
Simpson's Paradox
a comparison that holds for all of several groups can disappear or even reverse directions when the data are combined to form a single group
Lurking Variable
a variable that is not considered that affects the result
What causes paradox (in simpson's paradox)
A lurking variable
Trimmed Mean
discarding a certain percentage of lowest and highest values and then average the remaining values
Measuring
involves assigning a number to represent the property
Instruments
tests or survey used to make a measurement
Variable
the result of the measurement that can be different values for different people
Validity
does the instrument (test) measure what you are trying to measure
Test should reflect ..
actual knowledge or performance not test- taking skills or memorization
Content Validity
degree to which a test contains a representative selection of subject matter which students are expected to know
Predictive Validity
degree to which test predicts performance in other area related to property being measured
Construct Validity
degree to which test measures a construct (psychological concept such as intelligence or anxiety)
Overall English efficiency
Example of construct validity
A math test wouldn't be representative if you're being tested english
Example of content validity
Bias
systematic error that occurs every time a measurement is made (systematically wrong in the same direction)
Random Error
repeated measurements on the same individual give different results, error due to factors which we cannot predict
Reliability
results are repeated (consistent) over time
Mean determines ..
the center of the distribution; half the area of curve lies above and half lies below
Standard Deviation determines ..
the shape (mound or more peaked) of the curve
the more peaked the curve is
The lower the Standard Deviation
Standard Scores
observations expressed in standard deviations above or below the mean of a distribution
Positive Correlation
Increase in (Y) = Increase in (X) OR
Decrease in (Y) = Decrease in (X)
Negative Correlation
Increase in (Y) = Decrease in (X) OR Vice Versa
Scatter plot
shows the relationship of two quantitative variables measured on the same unit
Y =
dependent variable
a =
intercept + value of y when x is 0
x =
independent variable
b =
what you want to change
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