Unit 1: Data Collection & Desciptive Statistics Flashcards
Hypotheses must be…
Testable and falsifiable
In an equation, what is
n
Sample size
In an equation, what is
Σ
Sum (add the values)
Σ is the capital Greek letter sigma
In an equation, what is
xi
Individual data points
In an equation, what is
s or σ
Standard deviation
σ is the lower case Greek letter sigma
In an equation, what is
SEx̄
Standard Error of the Mean (also called “standard error”)
In an equation, what is
x̄
Mean
Pronounced “x bar”
Explaining the meaning of:
x̄
The average of the values
Explaining the meaning of:
s or σ
The average spread of the sample data around the mean
Explaining the meaning of:
SEx̄
How far from the sample mean the actual population mean is 68% likely to be
Explaining the meaning of:
95% confidence
How far from the sample mean the actual population mean is 95% likely to be
What does this image show?
Normal distribution
Describe all important statistics in this image
Highest point = mean, median, and mode
s = standard deviation
What percentage of samples are expected to fall in the red area?
50%
What percentage of samples are expected to fall in the red area?
x̄ ± 1s = 68%
What percentage of samples are expected to fall in the red area?
x̄ ± 2s = 95%
Consider the following for a normally-distributed sample:
- x̄ = 10
- s = 3
- n = 100
- SEx̄ = 0.3
What can you determine about the sample?
The mean sample value is 10.
68 individuals fell between 7 and 13
95 individuals fell between 4 and 17
Consider the following for a normally-distributed sample:
- x̄ = 10
- s = 3
- n = 100
- SEx̄ = 0.3
What can you determine about the population?
There is a 68% chance the population mean falls between 9.7 and 10.3
and a 95% chance the population mean falls between 9.4 and 10.6
Compare
Sample and Population
Sample (n) is a subset of the population (N), and the goal is to have the sample be representative of the population
What are the
Two Types of Data
Qualitative
and
Quantitative
Types of
Quantitative Data
Raw data are directly measured / counted
Manipulated data are calculated based on raw data
Examples of
Manipulated data
Mean, rates, and other statistical measures
What should all tables contain?
- Descriptive title that would allow the table to be understood even in absence of other information
- Headers with units!
- Data that has consistent decimal places and no units (already in the header)
How to convert from base unit to milli
Ex: 5 liters → ? mL
Multiply by 1,000
i.e. Move decimal to the right three places
5 L = 5,000 mL
How to convert from milli to micro
Ex: 5 mL → ? μL
Multiply by 1,000
i.e. Move decimal to the right three places
5 mL = 5,000 μL
How to convert from base unit to micro
Ex: 5 liters → ? μL
Multiply by 1,000,000
i.e. Move decimal to the right six places
5 L = 5,000,000 μL
How to convert from milli to base unit
Ex: 5 mL → ? L
Divide by 1,000
i.e. Move decimal to the left three places
5 mL = 0.005 L
How to convert from micro to base unit
Ex: 5 μL → ? L
Divide by 1,000,000
i.e. Move decimal to the left six places
5 μL = 0. 000 005 L
How to convert from micro to milli
Ex: 5 μL → ? mL
Divide by 1,000
i.e. Move decimal to the left three places
5 μL = 0.005 mL
List
Three measures of Central Tendency
Mean (x̄) - average
Median - middle value
Mode - most common
List
Two Measures of Variability
Range
Standard deviation (s or σ)
What can increase confidence?
Remember: increasing confidence means lowering the confidence interval
Having a larger sample size
When the sample’s standard deviation is lower (note: this is just a characteristic of a set of data and cannot be affected by changing the sample size)
Define
Rate
Manipulated data that divides two different units;
Usually some quantity / measurement divided by time
In an equation, what is
Δ
Change in
Value after - value before
Δ is the capital Greek letter delta
Importance of
Percent Change
Allows you to compare changes that occur when the starting values differ
Ex: A loss of $100 in a person that starts with $1,000 versus one that starts with $1,000,000; there is a higher percent change in the person that only started with $1,000
How do you calculate percent change?
