Sampling & Study Design
Definition: Observes individuals and measures variables without assigning treatments.
Example: Studying health habits by surveying people rather than assigning diets.
What is Observational Study
Definition: Rejecting a true null hypothesis (false positive).
Example: Saying a new drug works when it doesn't.
What is Type I Error
Definition: Minimum, Q1, Median, Q3, Maximum.
Used to create boxplots.
What is Five-Number Summary
Definition: The group in an experiment that does not receive the treatment—used for comparison.
What is Control Group
Definition: A variable whose value is determined by chance.
Types: Discrete or continuous
What is Random Variable
Comparison - Use a control group
Random assignment - Reduces bias
Control - Reduce confounding variables
Replication - Use enough subjects to detect real effects
What is Principles of Experimental Design
Definition: The threshold for rejecting the null hypothesis.
Common values: 0.05, 0.01
What is Significance Level
Definition: The range between the first (Q1) and third (Q3) quartiles.
Formula: IQR = Q3 - Q1Use: Measures spread; helps identify outliers.
What is Inter Quartile Range (IQR)
Definition: Choosing individuals who are easy to reach. Often leads to bias.
Example: Surveying only friends about school lunch.
What is Convenience Sampling
Definition: A rule used to find the probability that either of two events occurs.
Formula: P(A or B) = P(A) + P(B) - P(A and B)
What is Addition Rule
Definition: A sampling method where the population is divided into groups, and entire clusters are randomly selected.
Example: Randomly choosing 3 school classes and surveying everyone in them.
What is Cluster Sample
Definition: Failing to reject a false null hypothesis (false negative).
Example: Saying a drug doesn't work when it actually does.
What is Type II Error
Definition: A measure of how spread out the data is from the mean.
What is Standard Deviation
Definition: A variable that affects both the explanatory and response variable, making it hard to determine causation.
Confounding Variable
Definition: As the sample size increases, the sample mean gets closer to the population mean.
Example: The more times you flip a fair coin, the closer the proportion of heads gets to 0.5.
What is Law of Large Numbers
Definition: Divide population into groups, then randomly sample from each.
Example: Sampling students from each grade level.
What is Stratified Random Sample
Definition: The probability of getting results as extreme (or more) as observed, assuming the null hypothesis is true.
What is P-Value
Definition: The value below which a certain percent of data falls.
What is Percentile
Definition: When some groups are left out or underrepresented in a sample.
What is Undercoverage
Definition: The probability that an event does not happen.
Formula: P(not A) = 1 - P(A)
What is Complement
Definition: A variable not included in the study that affects both explanatory and response variables.
Example: Ice cream sales and drowning deaths may both be influenced by temperature
What is Lurking Variable
Definition: The probability of correctly rejecting a false null hypothesis (avoiding a Type II error).
What is Power
Definition: A measure strongly affected by outliers or skewness.
What is Nonresistant Measure
Definition: Keeping subjects or researchers unaware of the treatment group to avoid bias.
What is Blinding
Definition: Probability of one event given that another event has occurred.
Formula: P(A|B) = P(A and B) / P(B)
What is Conditional Probability