Summary Stats, Distributions, and Central Limit Theorem Flashcards
What is data reduction?
reduces bits of data
Frequency distribution?
a chart that summarizes data in terms of the frequencies of a variable value
- a simple tally or chart
- can be used w/ continuous or categorical data. Bar chart is categorical. Histogram is continuous.
Cumulative frequencies?
The totals broken up equal to the sum of a class;
Ex: 11100100 missing 0 (1=female; 0=male)
how many female?: 4/10= 0.4=40%
how many male?: 5/10= 0.5=50%
how many missing?: 1/10= 0.1=10%
What is a relative frequency?
The ratio of frequency of a particular event to the total frequency
-how many times a value of data keeps occurring
Frequencies can be computed for continuous variables T or F?
True
Measures of central tendency?
- mode
- median
- mean
Mode?
frequency of values
Mean?
the average of values
Median?
the middle value when all values are in order
Measures of variability?
-range
What is standard deviation?
the square root of the variance
-an indication of the dispersion of a variable
Variance?
average squared distance from the mean
Sample variance formula?
slide 54/78
What is a distribution?
It describes how values for a certain
standard deviation^2=
variance
distribution of continuous variables
ex: percentiles, probabilities
-25th percentile-
-50th percentile-
-75th percentile-
-first quatile
-second quartile (median)
-third quartile
-10th percentile-
-25th percentile-
-50th percentile-
-data point which 10% falls below
-data point which 25% falls below
-data point which 50% falls below
right skewed distribution implies what?
mean>median>mode
left skewed distribution implies?
mode>median>mean; opposite
sample distribution?
distribution of observed values in the sample
-sample mean and sample SD are denoted (x (w/ a hat on top), s)
they are stats or sample stats and describe the center and spread of this distribution
population distribution?
distribution of possible values from a population
-pop. mean and SD are denoted
-they are parameters that describe the center and spread of this distribution
sampling distribution?
distribution of a (sample) stat-especially, the distribution of x (w/ a hat on top)
-sample mean follows normal distribution w/ mean and standard deviation
