Lesson 2: Descriptive Statistics Flashcards
Population
the entire collection of people, animals, cells, or other things from which we collect data
Parameter
A number that is calculated from an entire population
Sample
A subset or group drawn from the population
Statistic
A number or quantity that is calculated from a sample of data
Descriptive Statistics
Statistics that describe the sample without attempting to generalize the results to other groups or populations
Inferential Statistics
Statistics that infer the likelihood that the results can be generalized to the population
Measure of Central Tendency
A single value that attempts to describe the central position of a set of data
Mean
Average Value
Median
Middle Value
Mode
Most frequent value
Measure of dispersion/variation
A value that describes how the data are dispersed around the measure of central tendency OR the extent to which individual values differ from the mean/median/mode
Standard Deviation
On average, how much individual values differ from the mean
Variance
How far a set of numbers is spread out from the mean
Range
The difference between the largest & smallest value in the data set
Interquartile Range
A measure of the “middle fifty” in the data set AKA the difference between first and third quartile of the data
Outlier
An observation point that is distant from other observations
Frequency
The number of times a value appears in the data set
Frequency Distribution
A table or graph that illustrates how frequently each value appears in the data set
Normal Distribution
A symmetric, bell-shaped distribution for a continuous variable
For a normal distribution.. __ % of observations fall within 1 standard devation, __ % of observations fall within 2 standard devations, and __ % of observations fall within 3 standard devations.
1 = 68% 2 = 95% 3 = 99.7%
Confidence Interval
An estimate of the population parameter that will contain the population mean a specified proportion of the time (usually 95% or 99%)
Probability
The likelihood that an event will occur
What descriptive data is NOT done for nominal data?
Median and Median (we just see frequency distributions and mode)
Statistics are sample values. What are their corresponding population values?
Parameters
What numbers describe the extent to which individual values differ from the mean?
Measures of dispersion
What does a standard deviation of 0 indicate?
All values in the data are the same.
In a normal distribution, what percentage of the values fall within two standard deviations of the mean?
95%
“What is your religion?” is a nominal scale measure. What measure of central tendency is appropriate to use in this instance?
Mode
One hundred participants answer the question, “How many songs did you download last week?” What is the appropriate measure of central tendency to use in this example?
Mean
What measure of dispersion is generally reported with the median?
Range
What describes the basic objective of descriptive statistics?
To summarize basic findings for the sample
What does it tell us if our P-value < Alpha?
The results are statistically significant.
