AP Biology Statistics and Experimental Design Flashcards

A complete set of vocabulary flashcards covering statistics, null and alternative hypotheses, confidence intervals, error bars, and experimental design principles from the lecture notes.

Null Hypothesis

A statistical hypothesis stating that there is no difference between groups or treatments, where any observed differences are the result of chance and differences between means are within $2\,SE_{\bar{x}}$.

Alternative Hypothesis

A statistical hypothesis stating that there is a difference between groups or treatments, where differences are the result of some nonrandom cause and differences between means are not within $2\,SE_{\bar{x}}$.

Reject vs. Fail to Reject

Statistical terminology used instead of 'accept' or 'prove' because an investigator can never be $100\%$ accurate that a sample truly represents the actual population.

Mean ($\bar{x}$)

The sum of all values in a data set divided by the total number of values; describes central tendencies but is heavily skewed by outliers.

Median

The middle value in a data set that has been arranged in ascending or descending order.

Minimum Value

The smallest mathematical value present in a data set.

Maximum Value

The largest mathematical value present in a data set.

Standard Deviation ($\sigma$ or $s$)

A measure of the amount of variation or dispersion in data, expressed in the same unit as the mean ($\bar{x}$).

Normal Distribution

A symmetrical, bell-shaped graph showing how data are distributed around the mean ($\bar{x}$) based on standard deviation ($s$).

68-95-99.7 Rule

The empirical rule for normal distributions stating that roughly $68\%$ of values lie within $1\,SD$ of $\bar{x}$, $95\%$ lie within $2\,SD$, and $99.7\%$ lie within $3\,SD$.

Standard Error of the Mean ($SE_{\bar{x}}$ or $SEM$)

A statistic measuring how accurately a sample mean represents the true population mean, calculated using $SE_{\bar{x}} = \frac{s}{\sqrt{n}}$.

Confidence Interval

An estimated range of values (such as a $95\%$ confidence interval spanning $\bar{x} \pm 2\,SEM$) in which there is high certainty that the true population mean lies.

Error Bars

Graphical lines drawn above and below a mean data point on a graph, typically extending $\pm 2\,SEM$, to represent precision or confidence intervals.

Overlapping Error Bars

A situation in graphical data where error bars overlap between groups, indicating that the difference in data is not statistically significant and likely due to chance.

Non-Overlapping Error Bars

A situation in graphical data where error bars do not overlap between groups, indicating that the difference in data is statistically significant and due to a nonrandom cause.

Hypothesis

A testable explanation of a phenomenon that leads to a prediction of experimental outcomes based on background research.

Independent Variable (IV)

The factor manipulated or changed by the experimenter, or the specific treatment groups chosen to study.

Dependent Variable (DV)

 The factor measured or observed as the experimental outcome in response to changes in the independent variable.

Experimental Group

The group or set of subjects in an experiment that receives the specific factor or condition being tested.

Control Group

A group used as a standard of comparison in an experiment, classified as either a positive or negative control.

Positive Control

An experimental control group treated with a condition known to produce an expected positive result, confirming that the setup, reagents, and equipment function properly.

Negative Control

An experimental control group expected to yield no response or a baseline outcome, helping confirm that observed positive results are truly due to the test condition rather than external factors.

Constants

Factors kept identical across all experimental and control groups to ensure a controlled experiment.

Trials

The number of times an experimental procedure is repeated or the sample size tested per group, where higher numbers reduce the impact of errors.

Pyrethroid Insecticides

A class of chemical insecticides, such as deltamethrin and permethrin, used to test mosquito mortality and resistance across varying regional usage levels.