1. Quantitative Skills : Graphing
Ms. Navarro’s AP Biology

2. Categories of data:
Qualitative data is not numerical and is usually subjective.
Quantitative data is numerical and lends itself to statistical analysis.
1st Period
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3. Quantitative data can be either discrete or continuous.
Discrete data has finite values, such as integers, or bucket categories such as “red” or “tall”.
Continuous data has an infinite number of values and forms a continuum.

4. Which graph shows continuous data and which graph shows discrete data?
Graph A
Graph B
Graph B is discrete and Graph A is continuous

5. One of the first steps in data analysis is to create graphical displays of the data. Visual displays can make it easy to see patterns and can clarify how two variables affect each other.
AP Biology Quantitative Skills Manual

6. Line Graphs
Used when data on both scales of the graph (the x and y axes) are continuous.
The dots indicate measurements that were actually made.

7. Basic Traits of A Good Graph
1. A Good Title
A good title is one that tells exactly what information the author is trying to present with the graph.
Relation Between Study Time and Score on a Biology Exam in 2011
-or-
Study Time vs. Score on a Biology Exam in 2011
AP® Biology Investigative Labs: An Inquiry-Based Approach
3rd

8. Basic Traits of A Good Graph
Axes should be consistently numbered.
Axes should contain labels, including units.
AP® Biology Investigative Labs: An Inquiry-Based Approach
2nd period

9. Basic Traits of A Good Graph
A frame should be put around the outside of the graph.
AP® Biology Investigative Labs: An Inquiry-Based Approach

10. Basic Traits of A Good Graph
The independent variable is always shown on the x axis.
The dependent variable is always shown on the y axis.
Dependent
Variable
AP® Biology Investigative Labs: An Inquiry-Based Approach
Independent
Variable

11. Extrapolation is a prediction of what the chart might look like beyond the measured set of data. A broken line is used, indicating this a prediction and not data actually collected.

12. The slope of a line indicates the rate at which the variables being graphed are changing.
y y2 – y1
m = =
x x2 – x1
Rise
Slope =
Run

13. Positive Slope Negative Slope Zero Slope Rate Increasing
Rate Decreasing
Constant Rate
Indicates some values
were skipped

14. Line charts can be plotted with multiple data sets, allowing for better comparison.
Makes use of a legend

15. Statistics is the study of the collection, organization, analysis, interpretation and presentation of data. 

16. Population vs. Sample
Often, researchers want to know things about a population (N), but it may not be feasible to obtain data for every member of an entire population.
A sample (n) is a smaller group of members of a population selected to represent the population. The sample must be random.

17. If a sample is not collected randomly, it may not closely reflect the original population. This is called sampling bias.

18. A normal distribution, also known as a “bell curve” or “normal curve”, can be formed with continuous data.

19. The type of data being collected during an investigation should be determined before performing the actual experiment. The type of data will determine the statistical analyses that can be used.

20. Three Types of Data: Parametric data: data that fit a normal curve
Nonparametric data: data that do not fit a normal curve
Frequency or count data: generated by counting

21. Normal or parametric data
Measurement data that fit a normal curve or distribution.
Data is continuous, generally in decimal form.

22. Nonparametric data
Do not fit a normal distribution, may include large outliers
Can be qualitative data.

23. Frequency or count data
Generated by counting how many of an item fit into a category.
Can be data that are collected as percentages.
AP Biology Quantitative Skills Manual

24. Two Types of Descriptive Statistics:
Comparative statistics: compare variables
Association statistics: look for correlations between variables

25. Comparative statistics (Is A different from B?).
Bar Graph or
Pie Chart
Bar Graph
Box-and-Whisker Plot
Parametric Data
(normal data)
Nonparametric Data
Frequency
Data
(counts)

26. Association statistics associations between variables (How are A and B correlated?).
Scatterplot
Parametric Data
and
Nonparametric Data
AP Biology Quantitative Skills Manual

27. Bar Graphs
Used to visually compare two samples of categorical or count data.
AP Biology Quantitative Skills Manual

28. Histograms (Frequency Diagrams)
Used to display the distribution of data, providing a representation of the central tendencies and the spread of data.
AP Biology Quantitative Skills Manual

29. Creating a histogram requires setting up bins — uniform range intervals that cover the entire range of the data. Then the number of measurements that fit in each bin are counted and graphed.
AP Biology Quantitative Skills Manual

30. References: AP® Biology Investigative Labs: An Inquiry-Based Approach and AP® Biology Quantitative Skills: A Guide for Teachers