Quick Review Flashcards
What are the four common scales of measurement?
Nominal, Ordinal, Interval and Ratio
What is the main differences between an interval and a ratio scale?
Interval: values but they are equal
Ratio: there is an aboslute zero- one is always better then the other
The most important characteristic behind using different scales is to keep in mind the numbers themselves (T OR F)
false; what is important is the underlying variable that we hope that we are measuring
What is the practical distinction between discrete and continous variables?
Discrete variables take on only a few different values, but continous variables can take on any value between the lowest and highest score
What is the independent variable?
I: the variable is the one that is manipulated to get a result
what we are trying to study, as opposed to the score we obtain
To oversimplify, random selection is useful to ________ while random assignment is useful to ______
- assure that we can generalize to the population from which we sampled
- assure that differences between groups are not due to extranoues variables
When we refer to X , we are refering to
any specific variable
What is the general rule about parentheses in an equation?
DO IT FIRST
BEDMAS MOFO
THE NOTATION Σ MEANS:
THE SUM
What is the purpose of plotting data?
to make it interpretable
the endpoint of an interval are called
the real upper and lower limits
a figure that plots various values of the dependent variable on the X axis and the frequencies on the Y axis is called:
frequency distribution (histogram)
The optimal number of intervals for a histogram or a stem leaf is:
whatever makes the most sense and is the most useful for that specific data set
^^ how fucking helpful
List three important things about stem leaf plot
used to present the shape and the values of score, back to back to show two related scores and adjusted to handle different sized values
List the three terms that describe the shape of a distribution
symmetry modality and skewness
a positively skewed distrubition has a tail stretching out to the right T OR F
T
A MAJOR CHARACTERISTIC OF A GOOD GRAPHIC IS
SIMPLICITY
Which of the measures of central tendency are you most likely to see everywhere?
the mean
What do we report when a distribution has two distinct and non adjacent modes
REPORT BOTH PEAKS (BI-MODAL) - both significantly large but maybe not the same
When is the median most useful?
when we dont want the extreme score to influence the result
Give two advantages to the mean
more stable estimate of the central tendency of the population in over-repeated sampling and it can be algebraically
Why do we use trimmed samples
To eliminate the influence of extreme scores
What is a good percentage to trim?
10-20%
Define an outlier
an extreme and unusual score on a box plot
what is the major prob with IQR
it deletes so many observations that eliminates alot of the varibility
how would you describe the IQR with respect to trimmed samples?
25% trimmed sample
what is wrong with the average deviation from the mean?
its always gonna be 0
why is the standard deviation a better measure then the variance when we are describing data?
the variance measure presented in terms of squared units, where as the standard deviation s presented in terms of the unit of measurement themselves
why do we divide n-1 instead of N when we are computing standard deviation and variance
gives us an unbiased estimate of the population
Sample divide by n-1
Population divide by just 1
n-1 is known as the
degree of freedom
what is the quartile location?
they are points that cut off teh first and 3rd quarter
how do we determine the values that will end of the whiskers
they are values that are no more then 1.5 times the IQR
what is the winsorized sample?
one in which the trimmed values are replaced by the largest and smallest values that remain
Ordinate means
y axis
what is special about standard normal distribution
its mean is 0 and its standard deviation is always 1
what do the following represent
N:
μ:
σ
N: Number of values in data set
μ: Mean of population (sum divided by N)
σ: standard deviation of population
Z scores represent:
the number of standard deviations above or below the mean
what do we mean by standardization?
the process of transforming a raw score to a scale with a specified mean and variance
What are the means and SD of a t score?
50 and 10
