2.8: Descriptive v Inferential Statistics Flashcards
Descriptive Statistics
Techniques to organize and summarize data collected from a sample.
Sample Statistics
Numeric summaries of our sample
What are 3 examples of sample statistics?
- Central tendency measures
- Variability
- Pearson Correlation
What is the symbol for mean in a sample?
X-bar
What is the symbol for variance in a sample?
s^2
What is the symbol for standard deviation in a sample?
s
What is the symbol for Sum of Squares in a sample?
SS
What is the symbol for correlation in a sample?
r
What is the symbol for z score in a sample?
z
What are two measures that can be conducted for samples but not population?
- Sum of squares (SS)
- Z Score
What can you use descriptive statistics for?
To analyze a sample by first calculating the mean and standard deviation
Point Estimate
A single estimate of a population value based on data from a sample.
What are 3 point estimate measurements?
- Frequency
- Central tendencies
- Pearson Correlation
Inferential statistics
Techniques based on probability to make conclusions about the population based on data from a sample.
What does inferential statistics give us?
More information about the population from a standard sample.
Population Parameters
Numeric summaries of our entire population (UNKNOWN)
Population
Entire set of things we want to understand
Inference
The process of drawing conclusions about population parameters based on a sample taken from the population
What is the symbol for mean in a population?
μ(mu)
What is the symbol for variance in a population?
𝝈 (sigma squared)
What is the symbol for standard deviation in a population?
𝝈(sigma)
What is the symbol for correlation in a population?
ρ(rho)
Confidence Interval (CI)
A range of how precise our point estimate is by capturing a range that VERY OFTEN contains the true population value
What does a 95% confidence interval mean?
It contains the true population mean 95% of the time.
How do you state an analysis of a 95% confidence interval?
“If we ran a confidence interval 95% of the time, then 95% of that time the range would contain the true mean of the population.”
What happens to our confidence on margin of error as sample size increases?
Our level of confidence increases
What happens when the confidence interval overlaps with 0?
No relationship can be determined between the variables
What are two factors that affect precision/
- Sample size
- Variability level
How does sample size lead to more precise estimates?
The larger the sample size, the higher the precision
How does variability lead to more precise estimates?
Lower variability leads to higher precision
When can we not obtain detailed measurements?
When there is only inferred statistical values (not precise)
What adjustment is needed for an accurate population estimate?
degrees of freedom
