AP Biology Scientific Method and Statistics Review

Comprehensive practice flashcards covering AP Biology core principles, scientific practices, experimental design, variables, control types, central tendencies, and statistical measures.

What are the four Big Ideas that serve as the foundation of AP Biology?

Big Idea 1: Evolution (drives diversity and unity of life), Big Idea 2: Energetics (use of energy and molecular building blocks), Big Idea 3: Information storage and transmission (storing, retrieving, transmitting, and responding to info), and Big Idea 4: Systems interactions (complex properties of biological interactions).

What is the difference between inductive reasoning and deductive reasoning?

Inductive reasoning derives generalizations from a large number of specific observations, whereas deductive reasoning derives specific results from general premises.

What is a null hypothesis ($H_0$)?

A null hypothesis is a statement that the researcher tries to disprove, reject, or nullify; it states that there is no difference between two groups of data and that any observed experimental differences are due to chance.

Why should a researcher never state that a hypothesis is "correct"?

Hypotheses can be supported or disproven by experimental observations and data, but they can never be proven true.

How do a scientific hypothesis, theory, and law differ from one another?

A hypothesis is a testable explanation for an observation; a theory summarizes a broad group of hypotheses supported by a massive body of evidence; and a scientific law is a statement of fact (often expressed as a mathematical formula) that describes an observation without explaining "how" or "why".

What is the minimum accepted number of experimental trials in the scientific community?

The minimum accepted number of trials is $3$.

What is the distinction between an independent variable and a dependent variable?

An independent variable is the single factor manipulated or changed by the experimenter, while a dependent variable is the factor measured to determine the outcome that depends on the manipulation of the independent variable.

Why is it important to change ONLY the independent variable in an experiment?

If you measure a change in the dependent variable while changing multiple factors, you will not know whether it is the independent variable or an uncontrolled variable causing the change.

What is the role of a positive control group in an experiment?

A positive control group is exposed to a treatment known to produce the expected effect rather than the experimental treatment, ensuring that the experimental setup is capable of producing a result when one should occur.

What is the role of a negative control group in an experiment?

A negative control group is exposed to no treatment or a treatment known to have no effect, setting a baseline to ensure that no outside confounding variables or biases affect the experimental outcome.

Are experimental controls identical to constants?

No, controls are comparison groups used to eliminate errors and validate data, whereas constants are factors kept identical across all experimental and control groups throughout the experiment.

Which measure of central tendency is best for data sets containing extreme outliers, and why?

The median, because it is determined by arranging data in numerical order and identifying the middle value, preventing distortion from extreme high or low measurements.

How is the range of a data set calculated, and what does it indicate?

Range is calculated by subtracting the smallest value from the largest value in a data set; a larger range indicates greater spread and variability in the data.

What does a low standard deviation ($s$) suggest about an experimental dataset?

A low standard deviation indicates that the data points are clustered closely around the mean, suggesting that the independent variable is likely causing the observed changes.

What is the formula for sample standard deviation ($s$)?

$$s = \sqrt{\frac{\sum (x_i - \bar{x})^2}{n - 1}}$$

How are the degrees of freedom calculated in the sample standard deviation formula?

Degrees of freedom are calculated as $n - 1$, where $n$ is the total number of data values in the sample.

What does the Standard Error of the Mean ($SE_{\bar{x}}$) measure?

Standard Error of the Mean measures the precision of and confidence in the sample mean, indicating how well the sample mean represents the true mean of the general population.

What is the formula for calculating Standard Error of the Mean ($SE_{\bar{x}}$)?

$SE_{\bar{x}} = \frac{s}{\sqrt{n}}$, where $s$ is the standard deviation and $n$ is the sample size.

What does it mean if the standard error bars of two sample groups overlap on a graph?

If the error bars overlap, the difference between the two sample means is not statistically significant.

What does it mean if the standard error bars of two sample groups do not overlap on a graph?

If the error bars do not overlap, the difference between the two sample means may be statistically significant.

For tomato plant height measurements ($n = 5$) of $65\,mm$, $52\,mm$, $71\,mm$, $56\,mm$, and $61\,mm$, what is the mean plant height?

The mean height is $61\,mm$ (calculated as $\frac{65 + 52 + 71 + 56 + 61}{5} = \frac{305}{5} = 61\,mm$).

Given a sample standard deviation $s = 7.45$ and sample size $n = 5$, what is the calculated Standard Error of the Mean ($SE_{\bar{x}}$)?

$SE_{\bar{x}} \approx 3.3$ (calculated as $\frac{7.45}{\sqrt{5}} \approx \frac{7.45}{2.236} \approx 3.3$).