Exam 1 Flashcards
Scale Variable
A continuous variable where magnitude and order matter
Ordinal Variable
a categorical variable where the order matters but not the magnitude (ex. 1 is below average, 2 is average, and 3 is above average)
Nominal Variable
A categorical variable where order and magnitude don’t matter (ex. 1 is female, 2 is male)
Population
All members of interest
Sample
a sub group of members of interest
Population Mean Symbol
μ
Variance of population symbol
σ^2
Standard deviation of population symbol
σ
Sample mean symbol
x bar
Sample variance symbol
s^2
Sample standard deviation symbol
s
Is the word “data” plural or singular
plural
Sampling Error
Difference between the sample and the actual population
Which is better for skewed data: mean or median?
Median, because each data point has the same weight as another data point and is less impacted by outliers.
Positive skew
Hump is on the left and the tail is being pulled right
Negative Skew
Hump is on the right and the tail is being pulled left
Which gives you more information: covariance or correlation?
Both tell you what direction the variables go (together or opposite) but correlation gives you the magnitude of the direction they move together or apart in.
Why do we use n-1 for sample calculations?
Accounts for the fact that there is some bias in the sample
What does the sum of squares show?
Shows the total spread around the mean
0.0-0.2
Very Weak Correlation Size of r
0.2-0.4
Weak correlation size of r
0.4-0.6
moderate correlation size of r
0.6-0.8
strong correlation size of r
0.8-1.0
very strong correlation size of r
What are the 4 assumptions of a pearson correlation?
linearly related, continuous scale variable, normal distribution, no significant outliers
What does IQR tell us and why is this better than range?
IQR is the range between 25th-75th percentile. This is better than range because it trims out the bottom and top 25%
Why do we square root the variance?
to get back to the original units
How many scores are within +/-1 SD in a normal distribution?
2/3
How many scores are within +/-2 SD in a noraml distribution
95%
How many scores are within +/-3 SD in a normal distribution
99.7%
What is a standardized distribution?
a predetermined standard deviation and mean
Cross-sectional study
looking at data from a single point in time
Randomized controlled trial
randomly assigning people to a group with a control group and a test group
Case Report
Serve to convey information to others and to catalog new ideas and information. Doesn’t contain high quality evidence.
Prospective cohort study
observational and following a group of people into the future
Case Control
anytime you’re seeing matching.
Meta analysis
collecting and reviewing all relevant papers
